drm/msm/mdp4: Support NV12MT format in mdp4

Using fb modifier flag, support NV12MT format in MDP4.

v2:
- rework the modifier's description [Daniel Vetter's comment]
- drop .set_mode_config() callback [Rob Clark's comment]
v3:
- change VENDOR's name and restrict usage to NV12 [pointed by Daniel]

Signed-off-by: Rob Clark <robdclark@gmail.com>

include/uapi/drm/drm_fourcc.h

@@ -207,4 +207,19 @@
  */
 #define I915_FORMAT_MOD_Yf_TILED fourcc_mod_code(INTEL, 3)
 
+/*
+ * Tiled, NV12MT, grouped in 64 (pixels) x 32 (lines) -sized macroblocks
+ *
+ * Macroblocks are laid in a Z-shape, and each pixel data is following the
+ * standard NV12 style.
+ * As for NV12, an image is the result of two frame buffers: one for Y,
+ * one for the interleaved Cb/Cr components (1/2 the height of the Y buffer).
+ * Alignment requirements are (for each buffer):
+ * - multiple of 128 pixels for the width
+ * - multiple of  32 pixels for the height
+ *
+ * For more information: see http://linuxtv.org/downloads/v4l-dvb-apis/re32.html
+ */
+#define DRM_FORMAT_MOD_SAMSUNG_64_32_TILE	fourcc_mod_code(SAMSUNG, 1)
+
 #endif /* DRM_FOURCC_H */