encoder: h264: fix level when bitrate is automatically computed.
encoder: h264: fix level when bitrate is automatically computed.

Fix level characterisation when the bitrate is automatically computed
from the active coding tools. i.e. ensure the bitrate once the profile
is completely characterized but before the level calculation process.

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