Revert "Makefile: Explicitly set '-std=c99'"

This reverts commit 5e5c3f15efe262ff23642dd543faf6a9dbb3bbdb.

Reason for revert: Breaks building on PowerPC, NetBSD, DJGPP, and it is
possible that SPARC fails to build as well.

Change-Id: I57b5125207de3fd156dface67cba605da893d6aa
Signed-off-by: Angel Pons <th3fanbus@gmail.com>
Reviewed-on: https://review.coreboot.org/c/flashrom/+/52425
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Anastasia Klimchuk <aklm@chromium.org>
Reviewed-by: Edward O'Callaghan <quasisec@chromium.org>
Reviewed-by: Nico Huber <nico.h@gmx.de>
2 files changed