ath9k: interleaved NF calibration on AR9002

NF calibration and other elements of long calibration are usually faster
than ADCs & I/Q calibrations due to independence of receiption of the
OFDM signal. Moreover sometime I/Q calibration can not be completed at
all without preceding NF calibration. This is due to AGC, which has a
habit to block a weak signal without regular NF calibration. Thus, we do
not need to deferr the long calibration forever.

So, if the long calibration is requested, then deferr the ADCs & I/Q
calibration(s) and run the longcal (the NF calibration in particular) to
obtain fresh noise data.

Run tested with AR9220.

Signed-off-by: Sergey Ryazanov <ryazanov.s.a@gmail.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/20200424004923.17129-5-ryazanov.s.a@gmail.com