commands/hwclock: align -n option help ...

Help string for hwclock -n option isn't aligned:

  barebox@barebox sandbox:/ help hwclock

  hwclock - query or set the hardware clock (RTC)

  Options:
          -f NAME                         RTC device name (default rtc0)
          -e VARNAME                      store RTC readout into variable VARNAME
          -n NTPSERVER            set RTC from NTP server
          -s ccyymmddHHMM[.SS]            set time

Signed-off-by: Antony Pavlov <antonynpavlov@gmail.com>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

commands: exit on invalid option ...

Barebox commands should not perform any action and return 0 if an
invalid parameter was given. This might cause undetected unintended
behvaior when calling commands with wrong options, either manually or
from a script.

Signed-off-by: Enrico Jorns <ejo@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

commands/hwclock: Check return value of rtc_read_time() ...

It is possible for rtc_read_time() to fill struct rtc_time it returns
with invalid values, so we have to check for its return value before
using returned time.

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

hwclock: Allow to set hwclock from sntp ...

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

hwclock command: forward return value of rtc_set_time ...

rtc_set_time can fail, forward the error to the user.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

hwclock command: use format like the Linux tool does ...

Print three-letter abbreviations of the days and months.

With a fixup by Andrey Smirnov:
| common/date.c: Fix off-by-one error
|
| As per http://pubs.opengroup.org/onlinepubs/007908775/xsh/time.h.html
| 'tm_wday' is zero indexed with zero representing Sunday, this is also
| corroborated by the code in rtc_time_to_tm() which used 4 to represent
| Thursday.

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

commands: add hwclock ...

The hwclock command allows to query or set the hardware clock (RTC).

Barebox' 'hwclock' command uses busybox' 'date' compatible
time format ccyymmddHHMM[.SS]:

  # /bin/busybox date -s 201407292005.41 ; /bin/date
  Tue Jul 29 20:05:41 MSK 2014
  Tue Jul 29 20:05:41 MSK 2014

Signed-off-by: Antony Pavlov <antonynpavlov@gmail.com>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>