Extend the wifi HAL to add a new method in IWifiChip. This new method is
used for setting the TX power limit for meeting SAR requirements.
Bug: 62437848
Test: ./hardware/interfaces/update-makefiles.sh
Test: mmm -j32 hardware/interfaces/wifi/1.1
Change-Id: I8320a64812339f15cd88636505de0dfda18f0ebf