Copy stable/10@r272459 to releng/10.1 as part of
the 10.1-RELEASE process.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Copy head (r256279) to stable/10 as part of the 10.0-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Port over the AR9285 PA calibration and initial calibration code from
Linux ath9k.

The ath9k ar9002_hw_init_cal() isn't entirely clear about what
is supposed to be called for what chipsets, so I'm ignoring the
rest of it and just porting the AR9285 init cal path as-is and
leaving the rest alone. Subsequent commits may also tidy up the
Merlin (AR9285) and other chipset support.

Obtained from: Linux ath9k