Introduce a new wmi interface controls noise floor (NF) calibration
period via debugfs as firmware has introduced it on v10.2.

It allows users to modify frequency of NF calibration in millisecond
and changes RSSI reporting frequency consequently.
Short calibration period will trigger more frequent NF calibration,
so that RSSI reported in receive frames is more realistic.

Till now calibration was done at 30 seconds.

Signed-off-by: Peter Oh <poh@qca.qualcomm.com>
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>