sys: Remove $FreeBSD$: two-line .h pattern

Remove /^\s*\*\n \*\s+\$FreeBSD\$$\n/

spdx: The BSD-2-Clause-FreeBSD identifier is obsolete, drop -FreeBSD

The SPDX folks have obsoleted the BSD-2-Clause-FreeBSD identifier. Catch
up to that fact and revert to their recommended match of BSD-2-Clause.

Discussed with: pfg
MFC After: 3 days
Sponsored by: Netflix

sys/dev: further adoption of SPDX licensing ID tags.

Mainly focus on files that use BSD 2-Clause license, however the tool I
was using misidentified many licenses so this was mostly a manual - error
prone - task.

The Software Package Data Exchange (SPDX) group provides a specification
to make it easier for automated tools to detect and summarize well known
opensource licenses. We are gradually adopting the specification, noting
that the tags are considered only advisory and do not, in any way,
superceed or replace the license texts.

Set the antenna "config group" field.

The reference HAL pushes a config group parameter to the driver layer
to inform it which particular chip behaviour to implement.

This particular value tags it as an AR9285.

Remove the AR9285 specific structure for LNA diversity and use the HAL.

The AR9300 HAL update included the LNA diversity configuration information
so it can be used in the AR9485 configuration code.

Enable slow diversity combining for the AR9285.

Now that I understand what's going on - and the RX antenna array maps
to what the receive LNA configuration actually is - I feel comfortable
in enabling this.

If people do have issues with this, there's enough debugging now available
that we have a chance to diagnose it without writing it up as 'weird
crap.'

Tested:

* AR9285 STA w/ diversity combining enabled in EEPROM

TODO:

* (More) testing in hostap mode

Revert this erroneous commit and re-disable the AR9285 combined antenna
diversity.

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

Disable diversity combining support until I can get a firm answer
from Atheros as to what/when this is supposed to be enabled.

Using the default RX fast diversity settings seems to help quite
a bit.

Whilst I'm here, change the prototype to return HAL_BOOL rather than int.

Add the initial AR9285 PHY glue for supporting antenna diversity.
This code isn't currently used anywhere; it's just linked into the build.