MFC ath(4) potential memory disclosure fixes

[1] r327499: ath: fix memory disclosure from ath_btcoex_ioctl

The ath_btcoex_ioctl handler allocated a buffer without M_ZERO and
returned it to userland without writing to it.

The device has permissions only for root so this is not urgent, and the
fix can be MFCd and considered for a future EN.

[2] r327500: ath: fix possible memory disclosures in ioctl handlers

Apply the fix from r327499 to additional ioctl handlers.

Note: related fix in r327529 does not apply directly to stable/10 and
will be addressed in a followup commit.

Submitted by: Domagoj Stolfa <domagoj.stolfa@gmail.com> [1]
Reported by: Ilja van Sprundel <ivansprundel@ioactive.com> [1,2]
Reviewed by: adrian [1]
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

Initial AR9485/AR933x 1x1 LNA diversity work.

* Add the LNA configuration table entries for AR933x/AR9485
* Add a chip-dependent LNA signal level delta in the startup path
* Add a TODO list for the stuff I haven't yet ported over but
I haven't.

Tested:

* AR9462 with LNA diversity enabled

Migrate the LNA mixing diversity machinery from the AR9285 HAL to the driver.

The AR9485 chip and AR933x SoC both implement LNA diversity.
There are a few extra things that need to happen before this can be
flipped on for those chips (mostly to do with setting up the different
bias values and LNA1/LNA2 RSSI differences) but the first stage is
putting this code into the driver layer so it can be reused.

This has the added benefit of making it easier to expose configuration
options and diagnostic information via the ioctl API. That's not yet
being done but it sure would be nice to do so.

Tested:

* AR9285, with LNA diversity enabled
* AR9285, with LNA diversity disabled in EEPROM