* set SarBackOffHighResolution = true for support power index
  from 0 to 80 for setting backoff in 0.25 dB step

Bug: 170369474
Test: sending sar command with power cap index between 20 ~ 80 and
confirm the SAR backoff is workable.

Change-Id: I56d75abcff55e93554bf656fff164b861fe0e3c2