drm/fourcc: Add formats R8, RG88, GR88

The Kodi/XBMC developers want to transcode NV12 to RGB with OpenGL
shaders, importing the two source planes through
EGL_EXT_image_dma_buf_import. That requires importing the Y plane as an
R8 EGLImage and the UV plane as either an RG88 or GR88 EGLImage.

CC: Peter Frühberger <peter.fruehberger@gmail.com>
Cc: Rainer Hochecker <rainer.hochecker@onlinehome.de>
Cc: Benjamin Widawsky <benjamin.widawsky@intel.com>
Reviewed-by: Pekka Paalanen <pekka.paalanen@collabora.co.uk>
Signed-off-by: Chad Versace <chad.versace@intel.com>

include/uapi/drm/drm_fourcc.h

@@ -34,6 +34,13 @@
 /* color index */
 #define DRM_FORMAT_C8		fourcc_code('C', '8', ' ', ' ') /* [7:0] C */
 
+/* 8 bpp Red */
+#define DRM_FORMAT_R8		fourcc_code('R', '8', ' ', ' ') /* [7:0] R */
+
+/* 16 bpp RG */
+#define DRM_FORMAT_RG88		fourcc_code('R', 'G', '8', '8') /* [15:0] R:G 8:8 little endian */
+#define DRM_FORMAT_GR88		fourcc_code('G', 'R', '8', '8') /* [15:0] G:R 8:8 little endian */
+
 /* 8 bpp RGB */
 #define DRM_FORMAT_RGB332	fourcc_code('R', 'G', 'B', '8') /* [7:0] R:G:B 3:3:2 */
 #define DRM_FORMAT_BGR233	fourcc_code('B', 'G', 'R', '8') /* [7:0] B:G:R 2:3:3 */