drm/exynos/mixer: enable support for 1024x768 and 1280x1024 modes

Since HDMI can handle these modes despite of MIXER limitations let's
enable them.
Signed-off-by: Andrzej Hajda <a.hajda@samsung.com>
Reviewed-by: Tobias Jakobi <tjakobi@math.uni-bielefeld.de>
Signed-off-by: Inki Dae <inki.dae@samsung.com>

drivers/gpu/drm/exynos/exynos_mixer.c

@@ -1015,6 +1015,9 @@ static int mixer_mode_valid(struct exynos_drm_crtc *crtc,
 	    (w >= 1664 && w <= 1920 && h >= 936 && h <= 1080))
 		return MODE_OK;
 
+	if ((w == 1024 && h == 768) || (w == 1280 && h == 1024))
+		return MODE_OK;
+
 	return MODE_BAD;
 }