tools: kwbimage: Add support for DATA command also for v1 images

The DATA command is already supported by mkimage for v0 images, but not
for v1 images.

BootROM code which executes v1 images also supports DATA command via an
optional extended v1 header OPT_HDR_V1_REGISTER_TYPE.

Implement support for DATA command for v1 images.

Signed-off-by: Pali Rohár <pali@kernel.org>
Reviewed-by: Marek Behún <marek.behun@nic.cz>
Reviewed-by: Chris Packham <judge.packham@gmail.com>
Reviewed-by: Stefan Roese <sr@denx.de>
Tested-by: Chris Packham <judge.packham@gmail.com>