nb/intel/gm45: Add VBOOT support

Change-Id: I943723da7167a47f514eda19fb9b71b8f56c2d32
Signed-off-by: Arthur Heymans <arthur@aheymans.xyz>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/35997
Reviewed-by: Nico Huber <nico.h@gmx.de>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/northbridge/intel/gm45/Kconfig

@@ -28,6 +28,10 @@ config NORTHBRIDGE_SPECIFIC_OPTIONS # dummy
 	select PARALLEL_MP
 	select C_ENVIRONMENT_BOOTBLOCK
 
+config VBOOT
+	select VBOOT_STARTS_IN_BOOTBLOCK
+	select VBOOT_SEPARATE_VERSTAGE
+
 config CBFS_SIZE
 	hex
 	default 0x100000