tools: kwboot: Fix checking image header version

Function image_version() returns unsigned value, so it can never be
negative. Explicitly check for two supported image versions: v0 and v1.

Signed-off-by: Pali Rohár <pali@kernel.org>
Reviewed-by: Marek Behún <marek.behun@nic.cz>
Reviewed-by: Stefan Roese <sr@denx.de>
1 file changed