ath9k: Display calibration data piers in debugfs

Display per frequency calibration data in dump_modal
debugfs entry including reference power, voltage,
tx temperature and noise floor.

Example of chain 0 of OEM card (dump from modal_eeprom):
Chain 0
Freq	 ref	volt	temp	nf_Cal	nf_Pow	rx_temp
5180	-30	0	137	0	0	0
5320	-24	0	137	0	0	0
5500	-15	0	137	0	0	0
5620	-10	0	137	0	0	0
5700	-15	0	137	0	0	0
5745	-16	0	135	0	0	0
5785	-19	0	136	0	0	0
5825	-22	0	136	0	0	0

Example of a card with calibrated noise floor.
Chain 0
Freq	 ref	volt	temp	nf_Cal	nf_Pow	rx_temp
4890	-49	0	128	-107	-97	124
5100	-23	0	128	-101	-96	124
5180	-18	0	128	-101	-96	124
5300	-12	0	128	-102	-97	124
5500	-9	0	128	-101	-97	125
5640	-17	0	128	-101	-98	124
5785	-25	0	128	-101	-98	124
5940	-33	0	128	-106	-99	124

Signed-off-by: Wojciech Dubowik <Wojciech.Dubowik@neratec.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>