tools: kwboot: Split sending image into header and data stages

This change is required to implement other features in kwboot.

Split sending header and data parts of the image into two stages.

Signed-off-by: Pali Rohár <pali@kernel.org>
[ refactored ]
Signed-off-by: Marek Behún <marek.behun@nic.cz>
Reviewed-by: Stefan Roese <sr@denx.de>
2 files changed