libs: encoder: h264: set profile via capsfilter
libs: encoder: h264: set profile via capsfilter

Until now, the encoder ignored the profile in src caps and chose one
according with the given parameters. But the encoder must honor the
profile specifed in src caps.

This patch do that, and if the encoder needs to choose the profile,
it will do it by following these rules:

1\ If given parameters are not compatible with given profile, the
   encoder will bail out with an error.
2\ The encoder will choose the higher profile indicated in the
   src caps.

https://bugzilla.gnome.org/show_bug.cgi?id=757941

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