Set the TX Power Index

1. If Hardware Power Control is enabled

   1. Return, there's nothing to do
2. Save the Override setting
3. If the TX Power Index isn't -1 or -2
   1. -- TPI SET (TODO)

   2. Write FIXME to OFDM Table 0xC, offset 1

   3. Save the TX Power Index
   4. Adjust Baseband Local Oscillator Cancel