tools: kwboot: Round up header size to 128 B when patching

tools: kwboot: Round up header size to 128 B when patching

The beginning of image data must be sent in a separate xmodem block;
the block must not contain end of header with the beginning of data.

Therefore we need to ensure that the image header size is a multiple of
xmodem block size (which is 128 B).

Read the file into a malloc()ed buffer of enough size instead of
mmap()ing it. (If we are going to move the data, most of the pages will
be dirty anyway.) Then move the payload if header size needs to be
increased.

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>