ath10k: implement debugfs interface for Transmit Power Control stats
The Transmit Power Control (TPC) dump will show the power control values for
each rate which makes it easier to debug calibration problems.
Example usage:
# cat /sys/kernel/debug/ieee80211/phy0/ath10k/tpc_stats
TPC config for channel 5180 mode 10
CTL = 0x10 Reg. Domain = 58
Antenna Gain = 1 Reg. Max Antenna Gain = 0
Power Limit = 34 Reg. Max Power = 34
Num tx chains = 3 Num supported rates = 155