DRM: ARC: PGU: add ARGB8888 format to supported format list

As we ignore first 8 bit of 32 bit pixel value we can add ARGB8888
format as alias of XRGB8888.
Signed-off-by: Eugeniy Paltsev <Eugeniy.Paltsev@synopsys.com>
Signed-off-by: Alexey Brodkin <abrodkin@synopsys.com>

drivers/gpu/drm/arc/arcpgu_crtc.c

@@ -23,6 +23,7 @@
 static const u32 arc_pgu_supported_formats[] = {
 	DRM_FORMAT_RGB565,
 	DRM_FORMAT_XRGB8888,
+	DRM_FORMAT_ARGB8888,
 };
 
 static void arc_pgu_set_pxl_fmt(struct drm_crtc *crtc)