libs: postproc: Modify src/sink template raw formats
libs: postproc: Modify src/sink template raw formats

We need to provide more precise template caps for postproc's src
and sink pads. The GST_VIDEO_FORMATS_ALL make all video formats
available which are really superfluous.

ceyusa/gstreamer-vaapi,GStreamer/gstreamer-vaapi,ceyusa/gstreamer-vaapi,GStreamer/gstreamer-vaapi