mb/google/brya: Add GPIO stubs

Add stubbed out GPIO configuration and perform GPIO initialization
during bootblock and ramstage.

BUG=b:174266035
TEST=Build Test

Signed-off-by: Eric Lai <ericr_lai@compal.corp-partner.google.com>
Change-Id: Ia658ab4b466242cf8658abb239f19a9c0a03849a
Reviewed-on: https://review.coreboot.org/c/coreboot/+/48065
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Tim Wawrzynczak <twawrzynczak@chromium.org>
diff --git a/src/mainboard/google/brya/Kconfig b/src/mainboard/google/brya/Kconfig
index f538ade..3c08757 100644
--- a/src/mainboard/google/brya/Kconfig
+++ b/src/mainboard/google/brya/Kconfig
@@ -26,4 +26,8 @@
 	string
 	default "brya" if BOARD_GOOGLE_BRYA0
 
+config VARIANT_DIR
+	string
+	default "brya0" if BOARD_GOOGLE_BRYA0
+
 endif # BOARD_GOOGLE_BASEBOARD_BRYA