drm: Drop the NV12M and YUV420M formats

The NV12M/YUV420M formats are identical to the NV12/YUV420 formats.
So just remove these duplicated format names.

This might look like breaking the ABI, but the code has never actually
accepted these formats, so nothing can be using them.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Inki Dae <inki.dae@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>

include/drm/drm_fourcc.h

@@ -107,8 +107,7 @@
 #define DRM_FORMAT_NV16		fourcc_code('N', 'V', '1', '6') /* 2x1 subsampled Cr:Cb plane */
 #define DRM_FORMAT_NV61		fourcc_code('N', 'V', '6', '1') /* 2x1 subsampled Cb:Cr plane */
 
-/* 2 non contiguous plane YCbCr */
-#define DRM_FORMAT_NV12M	fourcc_code('N', 'M', '1', '2') /* 2x2 subsampled Cr:Cb plane */
+/* special NV12 tiled format */
 #define DRM_FORMAT_NV12MT	fourcc_code('T', 'M', '1', '2') /* 2x2 subsampled Cr:Cb plane 64x32 macroblocks */
 
 /*
@@ -131,7 +130,4 @@
 #define DRM_FORMAT_YUV444	fourcc_code('Y', 'U', '2', '4') /* non-subsampled Cb (1) and Cr (2) planes */
 #define DRM_FORMAT_YVU444	fourcc_code('Y', 'V', '2', '4') /* non-subsampled Cr (1) and Cb (2) planes */
 
-/* 3 non contiguous plane YCbCr */
-#define DRM_FORMAT_YUV420M	fourcc_code('Y', 'M', '1', '2') /* 2x2 subsampled Cb (1) and Cr (2) planes */
-
 #endif /* DRM_FOURCC_H */