ratp: new reset command ...

E.g.:
    $ ./bbremote -v --port /dev/ttyUSB2 reset

Signed-off-by: Aleksander Morgado <aleksander@aleksander.es>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

ratp: new md and mw commands ...

This commit introduces support for running the md and mw commands
using the binary interface provided by RATP. This allows clients to
read and write memory files without needing to do custom string
parsing on the data returned by the console 'md' and 'mw' operations.

The request and response messages used for these new operations are
structured in the same way:

 * An initial fixed-sized section includes the fixed-sized
   variables (e.g. integers), as well as the size and offset of the
   variable-length variables.

 * After the initial fixed-sized section, the buffer is given, which
   contains the variable-length variables in the offsets previously
   defined and with the size previously defined.

The message also defines separately the offset of the buffer
w.r.t. the start of the message. The endpoint reading the message will
use this information to decide where the buffer starts. This allows to
extend the message format in the future without needing to break the
message API, as new fields can be appended to the fixed-sized section
as long as the buffer offset is also updated to report the new
position of the buffer.

E.g.:
    $ ./bbremote --port /dev/ttyUSB2 md /dev/pic_eeprom_rdu 0x107 5
    0000000000

    $ ./bbremote --port /dev/ttyUSB2 mw /dev/pic_eeprom_rdu 0x107 0102030405
    5 bytes written

    $ ./bbremote --port /dev/ttyUSB2 md /dev/pic_eeprom_rdu 0x107 5
    0102030405

    $ ./bbremote --port /dev/ttyUSB2 mw /dev/pic_eeprom_rdu 0x107 0000000000
    5 bytes written

    $ ./bbremote --port /dev/ttyUSB2 md /dev/pic_eeprom_rdu 0x107 5
    0000000000

Signed-off-by: Aleksander Morgado <aleksander@aleksander.es>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

ratp: implement generic command support ...

The RATP implementation now allows executing generic commands with a
binary interface: binary requests are received and binary responses
are returned.

Each command can define its own RATP request contents (e.g. to specify
command-specific options) as well as its own RATP response contents
(if any data is to be returned).

Each command is associated with a pair of numeric unique request and
response IDs, and for easy reference these IDs are maintained in the
common ratp_bb header. Modules may override generic implemented
commands or include their own new ones (as long as the numeric IDs
introduced are unique).

Signed-off-by: Aleksander Morgado <aleksander@aleksander.es>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

ratp: remove unused list pointer from ratp_bb_pkt ...

This struct type is used in the RATP FS implementation, but was never
used as a list element anywhere.

Signed-off-by: Aleksander Morgado <aleksander@aleksander.es>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

ratp: move barebox-specific command to ratp_bb.h ...

The ratp_run_command() is really an implementation detail of the
barebox ratp 'command' operation support. Move it to the barebox
specific header and rename it with the correct prefix.

Signed-off-by: Aleksander Morgado <aleksander@aleksander.es>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

barebox remote control ...

This adds the ability to control barebox over serial lines. The regular
console is designed for human input and is unsuitable for controlling
barebox from scripts since characters can be lost on both ends, the data
stream contains escape sequences and the prompt cannot be easily matched
upon.
This approach is based on the RATP protocol. RATP packages start with a
binary 0x01 which does not occur in normal console data. Whenever a
0x01 character is detected in the console barebox goes into RATP mode.
The RATP packets contain a simple structure with a command/respone
type and data for that type. Currently defined types are:

BB_RATP_TYPE_COMMAND (host->barebox):
	Execute a command in the shell
BB_RATP_TYPE_COMMAND_RETURN (barebox->host)
	Sends return value of the command back to the host, also means
	barebox is ready for the next command
BB_RATP_TYPE_CONSOLEMSG (barebox->host)
	Console message from barebox

Planned but not yet implemented are:

BB_RATP_TYPE_PING (host->barebox)
BB_RATP_TYPE_PONG (barebox->host)
	For testing purposes
BB_RATP_TYPE_GETENV (host->barebox)
BB_RATP_TYPE_GETENV_RETURN (barebox->host)
	Get values of environment variables

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
Tested-by: Andrey Smirnov <andrew.smirnov@gmail.com>