vboot: Provide declaration for verstage_mainboard_early_init()
Similar to bootblock, provide declaration for
verstage_mainboard_early_init() to support early mainboard
initialization if verstage is run before bootblock.
BUG=b:
155824234
TEST=Verified that trembyle still builds
Signed-off-by: Furquan Shaikh <furquan@google.com>
Change-Id: I106213ecc1c44100f1f74071189518563ac08121
Reviewed-on: https://review.coreboot.org/c/coreboot/+/41137
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Aaron Durbin <adurbin@chromium.org>