doc: add documentation for 'dfu' ...

Signed-off-by: Robert Schwebel <r.schwebel@pengutronix.de>

remove typedef cmd_tbl_t and replace it with struct command ...

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

rename U-Boot-v2 project to barebox ...

This has been done with the following script:

find -path ./.git -prune -o -type f -print0 | xargs -0 -r sed -i \
	-e 's/u2boot/barebox/g' \
	-e 's/U2Boot/barebox/g' \
	-e 's/U-boot V2/barebox/g' \
	-e 's/u-boot v2/barebox/g' \
	-e 's/U-Boot V2/barebox/g' \
	-e 's/U-Boot-v2/barebox/g' \
	-e 's/U_BOOT/BAREBOX/g' \
	-e 's/UBOOT/BAREBOX/g' \
	-e 's/uboot/barebox/g' \
	-e 's/u-boot/barebox/g' \
	-e 's/u_boot/barebox/g' \
	-e 's/U-Boot/barebox/g' \
	-e 's/U-boot/barebox/g' \
	-e 's/U-BOOT/barebox/g'

find -path ./.git -prune -o \( -name "*u-boot*" -o -name "*uboot*" -o -name "*u_boot*" \) -print0 | \
	xargs -0 -r rename 's/u[-_]?boot/barebox/'

It needs some manual fixup following in the next patch

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

commands: remove maxargs ...

No need to check for maximum argument counts. The commands are
safe to be called with more arguments, so lets safe some bytes.

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

call getopt_reset only once ...

instead of calling getopt_reset in each command,
call it only once before calling the command.

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

commands: return COMMAND_ERROR_USAGE ...

instead of calling u_boot_cmd_usage in each command to safe
space.

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

Add USB device support ...

This patch adds support for USB devices. It uses
the Linux Kernel gadget API. Along with this patch
comes driver support for the Freescale (arc) USB OTG
Core and USB Device Firmware Update (DFU)
The serial gadget support is not working at the moment.

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