drm: rcar-du: Enable compilation on ARM64

The R8A7795 SoC is ARM64-based and include a DU. Enable driver
compilation on ARM64.
Signed-off-by: Koji Matsuoka <koji.matsuoka.xm@renesas.com>
Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>

drivers/gpu/drm/rcar-du/Kconfig

 config DRM_RCAR_DU
 	tristate "DRM Support for R-Car Display Unit"
-	depends on DRM && ARM && OF
+	depends on DRM && OF
+	depends on ARM || ARM64
 	depends on ARCH_SHMOBILE || COMPILE_TEST
 	select DRM_KMS_HELPER
 	select DRM_KMS_CMA_HELPER