The sign of 'char' is not standardized and with GCC is architecture
dependent.
This fixes warnings when compiling this file on arm64.
Signed-off-by: Arthur Heymans <arthur@aheymans.xyz>
Change-Id: I53b99835b2ffec5d752fc531fd59e4715f61aced
Reviewed-on: https://review.coreboot.org/c/coreboot/+/76006
Reviewed-by: Felix Singer <service+coreboot-gerrit@felixsinger.de>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
62ea7a8165