guybrush: mark RO_GSCVD area unused

This area relates to storing of AP RO verification information.
CONFIG_VBOOT_GSCVD is enabled by default for TPM_GOOGLE_TI50 and
guybrush is using TPM_GOOGLE_CR50.

Signed PSP verstage has the FMAP embedded. Since CB:67376 shifted the
RO section up by 8K, they were misaligned. Hence marking this area as
unused instead of removing the same to work around ChromeOS
infrastructure shortcoming.

Signed-off-by: Himanshu Sahdev <himanshu.sahdev@intel.com>
Change-Id: Id852e5b5c1f777992a96a75143757f4df8d975b6
Reviewed-on: https://review.coreboot.org/c/coreboot/+/67901
Reviewed-by: Raul Rangel <rrangel@chromium.org>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/mainboard/google/guybrush/chromeos.fmd

@@ -22,6 +22,7 @@ FLASH@0xFF000000 16M {
 		RW_LEGACY(CBFS)
 		WP_RO@8M 8M {
 			RO_VPD(PRESERVE) 16K
+			RO_UNUSED 8K
 			RO_SECTION {
 				FMAP 2K
 				RO_FRID 64