libs: encoder: split set_context_info()
libs: encoder: split set_context_info()

Split set_context_info() adding init_context_info() which only
initialises the GstVaapiContextInfo structure inside GstVaapiEncoder
required for VAConfig.

https://bugzilla.gnome.org/show_bug.cgi?id=769266

Signed-off-by: Víctor Manuel Jáquez Leal <4955886a7d0bd82ff6afce9ed1e93fbb85ab8088@intel.com>

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