drm/rcar-du: Allow build with COMPILE_TEST=y

Allow rcar-du to be built with COMPILE_TEST=y for greater
coverage. Builds fine on x86/x86_64 at least.

Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Cc: Kieran Bingham <kieran.bingham+renesas@ideasonboard.com>
Cc: linux-renesas-soc@vger.kernel.org
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240408170426.9285-21-ville.syrjala@linux.intel.comReviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>

drivers/gpu/drm/renesas/rcar-du/Kconfig

@@ -2,7 +2,7 @@
 config DRM_RCAR_DU
 	tristate "DRM Support for R-Car Display Unit"
 	depends on DRM && OF
-	depends on ARM || ARM64
+	depends on ARM || ARM64 || COMPILE_TEST
 	depends on ARCH_RENESAS || COMPILE_TEST
 	select DRM_KMS_HELPER
 	select DRM_GEM_DMA_HELPER