libstagefright: HSR: Read framerate from HSR key

- HSR and HFR keys are made mutually exclusive now.
- In case of HSR, HSR key will be set with requested frame rate and
  HFR key is not set.
- In case of HFR, HFR key will be set with requested frame rate and
  HSR key is not set.
- Check
     if video-hfr key is set
        set kKeyHFR with HFR key value passed by camera
     else check video-hsr key, if set
        set kKeyHSR with HSR key value passed by camera

Change-Id: Ic7ad098137812ad78afdc326334fa390404075fc