Copy stable/9 to releng/9.3 as part of the 9.3-RELEASE cycle.

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

Copy head to stable/9 as part of 9.0-RELEASE release cycle.

Approved by: re (implicit)

Add some open-loop TX power debugging for AR9287.

Flesh out the TX power calibration for the AR9287.

I'm assuming for now that the AR9287 is only open-loop TX power control
(as mine is) so I've hard-coded the attach path to fail if the NIC is
not open-loop.

This greatly simplifies the TX calibration path and the amount of code
which needs to be ported over.

This still isn't complete - the rate calculation code still needs to be
ported and it all needs to be glued together.

Obtained from: Linux ath9k

Bring over my AR9287 work in progress.

It isn't linked into the build because it's missing the TX power
and PDADC programming code.

This code is mostly based on the ath9k codebase, compared against
the Atheros codebase as appropriate.

What's implemented:

* probe/attach
* EEPROM board value programming
* RX initial calibration
* radio channel programming
* general MAC / baseband setup
* async fifo setup
* open-loop tx power calibration

What's missing before it can be enabled by default:

* TX power / calibration setting code
* closed-loop tx power calibration routines
* TSF2 handling
* generic timer support from ath9k

Obtained from: Atheros, ath9k