mb/google/skyrim: Enable variants for Skyrim

BUG=b:214414033
TEST=builds
BRANCH=none

Signed-off-by: Jon Murphy <jpmurphy@google.com>
Change-Id: I034ab8a06842bee12060103b4a1bc4e3db69e42a
Reviewed-on: https://review.coreboot.org/c/coreboot/+/62145
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Raul Rangel <rrangel@chromium.org>
Reviewed-by: Karthik Ramasubramanian <kramasub@google.com>

src/mainboard/google/skyrim/Kconfig

@@ -33,6 +33,14 @@ config MAINBOARD_FAMILY
 config MAINBOARD_PART_NUMBER
 	default "Skyrim" if BOARD_GOOGLE_SKYRIM
 
+config OVERRIDE_DEVICETREE
+	string
+	default "variants/\$(CONFIG_VARIANT_DIR)/overridetree.cb"
+
+config VARIANT_DIR
+	string
+	default "skyrim" if BOARD_GOOGLE_SKYRIM
+
 config VBOOT
 	select VBOOT_NO_BOARD_SUPPORT
 	select VBOOT_SEPARATE_VERSTAGE