src/drivers/intel: Correct Kconfig option in Makefile

This Kconfig option was just added incorrectly, so would never add
the verstage.c file.

Signed-off-by: Martin Roth <martin@coreboot.org>
Change-Id: I4c39dca9d429ed786ea42c0d421d6ee815e8c419
Reviewed-on: https://review.coreboot.org/c/coreboot/+/47368
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Furquan Shaikh <furquan@google.com>
Reviewed-by: Angel Pons <th3fanbus@gmail.com>

src/drivers/intel/fsp1_1/Makefile.inc

@@ -4,7 +4,7 @@ ifeq ($(CONFIG_PLATFORM_USES_FSP1_1),y)
 
 verstage-y += car.c
 verstage-y += fsp_util.c
-verstage-$(CONFIG_SEPARATE_VERSTAGE) += verstage.c
+verstage-$(CONFIG_VBOOT_SEPARATE_VERSTAGE) += verstage.c
 
 bootblock-$(CONFIG_USE_GENERIC_FSP_CAR_INC) += cache_as_ram.S
 bootblock-y += fsp_util.c