Checksum is calculated by using 2s complement method. 8-bit sum of the
entire subpart directory from first byte of header to last byte of last
partition directory entry.
BUG=chrome-os-partner:53508
Change-Id: I991d79dfdb5331ab732bf0d71cf8223d63426fa8
Signed-off-by: Furquan Shaikh <furquan@google.com>
Reviewed-on: https://review.coreboot.org/15200
Tested-by: build bot (Jenkins)
Reviewed-by: Aaron Durbin <adurbin@chromium.org>