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spdx: The BSD-2-Clause-FreeBSD identifier is obsolete, drop -FreeBSD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

Add a method to explicitly disable radar reporting if required.

Change the ath_dfs_process_phy_err() method to take an mbuf rather than
a buffer pointer.

For large radar pulses, the AR9130 and later will return a series of
FFT results for software processing. These can overflow a single 2KB
buffer on longer pulses. This would result in undefined buffer behaviour.

Change the prototype so the radar enable can fail.

Remove the now unneeded references to these DFS methods.

Sorry for the noise everyone.

Approved by: re (kib, blanket)

Introduce some more DFS related hooks, inspired both by local work
and the Atheros reference code.

The radar detection code needs to know what the current DFS domain is.
Since net80211 doesn't currently know this information, it's extracted
from the HAL regulatory domain information.

The specifics:

* add a new ath_dfs API hook, ath_dfs_init_radar_filters(), which
updates the radar filters whenever the regulatory domain changes.
* add HAL_DFS_DOMAIN which describes the currently configured DFS domain .
* add a new HAL internal variable which tracks the currently configured
HAL DFS domain.
* add a new HAL capability, HAL_CAP_DFS_DMN, which returns the currently
configured HAL DFS domain setting.
* update the HAL DFS domain setting whenever the channel setting is
updated.

Since this isn't currently used by any radar code, these should all
be no-ops for existing users.

Obtained from: Atheros
Submitted by: KBC Networks, sibridge
Approved by: re (kib, blanket)

A few changes to make radar detection implementable in a hal_dfs/
module.

* If sc->sc_dodfs is set to 1 by the ath_dfs_radar_enable(),
set the relevant rx filter bit to begin receiving radar PHY
errors. The HAL code already knows how to set the relevant
error mask register to enable radar events.

* Add a missing call to ath_dfs_radar_enable() after ath_hal_reset()

* change ath_dfs_process_phyerr() to take a const char *buf for now,
rather than a descriptor. This way it can get access to the packet
buffer contents.

Flesh out the radar detection related operations for the ath driver.

This is in no way a complete DFS/radar detection implementation!
It merely creates an abstracted interface which allows for future
development of the DFS radar detection code.

Note: Net80211 already handles the bulk of the DFS machinery,
all we need to do here is figure out that a radar event has occured
and inform it as such. It then drives the DFS state engine for us.

The "null" DFS radar detection module is included by default;
it doesn't require a device line.

This commit:

* Adds a simple abstracted layer for radar detection state -
sys/dev/ath/ath_dfs/;
* Implements a null DFS module which doesn't do anything;
(ie, implements the exact behaviour at the moment);
* Adds hooks to the ath driver to process received radar events
and gives the DFS module a chance to determine whether
a radar has been detected.

Obtained from: Atheros