omxvideoenc: Filter out unimplemented formats
omxvideoenc: Filter out unimplemented formats

Don't announce pixel formats in the caps if they've not been
implemented.

varunkumara/test-repo,GStreamer/gst-omx,GStreamer/gst-omx,varunkumara/test-repo,CapOM/gst-omx,CapOM/gst-omx,CapOM/gst-omx,GStreamer/gst-omx,varunkumara/test-repo