encoder: h264: wrap pools for refs and frames reordering.
encoder: h264: wrap pools for refs and frames reordering.

Create structures to maintain the reference frames list (RefPool) and
frames reordering (ReorderPool) logic.

This is a prerequisite for H.264 MVC support.

Signed-off-by: Li Xiaowei <b8643d4267a7059f1ba46d491d58859933f0850a@intel.com>

CapOM/gstreamer-vaapi,01org/iotg-lin-gfx-gstreamer-vaapi,01org/iotg-lin-gfx-gstreamer-vaapi,gbeauchesne/gstreamer-vaapi,GStreamer/gstreamer-vaapi,GStreamer/gstreamer-vaapi,gbeauchesne/gstreamer-vaapi,ceyusa/gstreamer-vaapi,gbeauchesne/gstreamer-vaapi,CapOM/gstreamer-vaapi,01org/iotg-lin-gfx-gstreamer-vaapi,ceyusa/gstreamer-vaapi,CapOM/gstreamer-vaapi