wifi(hidl): Modify the SAR power levels interface

Modifying the interface used to lower the tx power level for meeting SAR
requirements based on recommendation from the nexus hardware team. The
previous interface passed in a single power value in dBm for meeting SAR
requirements. However, the SAR requirements are more complex than that.
Based on the connection mode (802.11 a,b,g,n,ac) and the number of
streams that are active (MIMO), the SAR power levels are very
different. Using the previous interface would mean that we will have to
use the lowest power level among all the connection modes to meet the SAR
requirements. This would however result in us lowering the power much
more than needed (~2 dBm) for many connection modes.
Instead, we're switching to a more generic interface where the framework
informs the wifi chip that we're entering a special tx power mode scenario
(today, there is only 1 for voice call). The chip can then lookup the
extensive table of power levels for different connection modes which are
pre-populated by the OEM's in the BDF file to set the power level (depending
on the scenario framework sends and the active connection mode).

Bug: 62437848
Test: Manual tests
Change-Id: I5ee3f0d2c130958dbeb352e3b5ad9407f432624f