Add VA API pixfmt (only VLD is available ATM).

Originally committed as revision 18309 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavcodec/mpegvideo.c

@@ -81,6 +81,7 @@ const enum PixelFormat ff_pixfmt_list_420[] = {
 };
 
 const enum PixelFormat ff_hwaccel_pixfmt_list_420[] = {
+    PIX_FMT_VAAPI_VLD,
     PIX_FMT_YUV420P,
     PIX_FMT_NONE
 };