vaapivideomemory: unroll gst_vaapi_video_allocator_free()
vaapivideomemory: unroll gst_vaapi_video_allocator_free()

Instead of having a gst_vaapi_video_memory_free() that is only going to
be called by gst_vaapi_video_allocator_free(), let's just remove the first
and merged into the second.

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