mm-video-v4l2: Add extended config to set instance priority

Enable priority as hinted by the client:
priority = 0 => real-time
         = 1 => non-realtime
Also add the android extension for priority and operating-rate

bug: 20131548
Change-Id: I4dbe6bd3c0c884648f626d07e56f0a7dc8fc04f0
6 files changed