drm/sun4i: Fix format mask in DE2 driver

Format mask is one bit too short. Fix it.

Fixes: 9d75b8c0 (drm/sun4i: add support for Allwinner DE2 mixers)
Signed-off-by: Jernej Skrabec <jernej.skrabec@siol.net>
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20171201060550.10392-2-jernej.skrabec@siol.net

drivers/gpu/drm/sun4i/sun8i_mixer.h

@@ -80,7 +80,7 @@
 
 #define SUN8I_MIXER_CHAN_UI_LAYER_ATTR_EN		BIT(0)
 #define SUN8I_MIXER_CHAN_UI_LAYER_ATTR_ALPHA_MODE_MASK	GENMASK(2, 1)
-#define SUN8I_MIXER_CHAN_UI_LAYER_ATTR_FBFMT_MASK	GENMASK(11, 8)
+#define SUN8I_MIXER_CHAN_UI_LAYER_ATTR_FBFMT_MASK	GENMASK(12, 8)
 #define SUN8I_MIXER_CHAN_UI_LAYER_ATTR_ALPHA_MASK	GENMASK(31, 24)
 #define SUN8I_MIXER_CHAN_UI_LAYER_ATTR_ALPHA_MODE_DEF	(1 << 1)
 #define SUN8I_MIXER_CHAN_UI_LAYER_ATTR_FBFMT_ARGB8888	(0 << 8)