drm/rcar-du: Add run-time dependencies

The Renesas R-Car Display Unit driver is only useful on shmobile
unless build testing. The LVDS output is useful on an even more
reduced hardware set.
Signed-off-by: Jean Delvare <jdelvare@suse.de>
Acked-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>

drivers/gpu/drm/rcar-du/Kconfig

 config DRM_RCAR_DU
 	tristate "DRM Support for R-Car Display Unit"
 	depends on DRM && ARM
+	depends on ARCH_SHMOBILE || COMPILE_TEST
 	select DRM_KMS_HELPER
 	select DRM_KMS_CMA_HELPER
 	select DRM_GEM_CMA_HELPER
@@ -12,6 +13,7 @@ config DRM_RCAR_DU
 config DRM_RCAR_LVDS
 	bool "R-Car DU LVDS Encoder Support"
 	depends on DRM_RCAR_DU
+	depends on ARCH_R8A7790 || ARCH_R8A7791 || COMPILE_TEST
 	help
 	  Enable support the R-Car Display Unit embedded LVDS encoders
 	  (currently only on R8A7790).