sys: Automated cleanup of cdefs and other formatting

Apply the following automated changes to try to eliminate
no-longer-needed sys/cdefs.h includes as well as now-empty
blank lines in a row.

Remove /^#if.*\n#endif.*\n#include\s+<sys/cdefs.h>.*\n/
Remove /\n+#include\s+<sys/cdefs.h>.*\n+#if.*\n#endif.*\n+/
Remove /\n+#if.*\n#endif.*\n+/
Remove /^#if.*\n#endif.*\n/
Remove /\n+#include\s+<sys/cdefs.h>\n#include\s+<sys/types.h>/
Remove /\n+#include\s+<sys/cdefs.h>\n#include\s+<sys/param.h>/
Remove /\n+#include\s+<sys/cdefs.h>\n#include\s+<sys/capsicum.h>/

Sponsored by: Netflix

sys: Remove $FreeBSD$: one-line .c pattern

Remove /^[\s*]*__FBSDID\("\$FreeBSD\$"\);?\s*\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spdx: The BSD-2-Clause-FreeBSD identifier is obsolete, drop -FreeBSD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

Mark more nodes as CTLFLAG_MPSAFE or CTLFLAG_NEEDGIANT (7 of many)

r357614 added CTLFLAG_NEEDGIANT to make it easier to find nodes that are
still not MPSAFE (or already are but aren’t properly marked).
Use it in preparation for a general review of all nodes.

This is non-functional change that adds annotations to SYSCTL_NODE and
SYSCTL_PROC nodes using one of the soon-to-be-required flags.

Mark all low hanging fruits as MPSAFE.

Reviewed by: markj
Approved by: kib (mentor, blanket)
Differential Revision: https://reviews.freebsd.org/D23626

sys: general 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.

No functional change intended.

[net80211] extend the net80211 ALQ code to support variable payloads.

Also - allow driver specific bits to be added, rather than just net80211.

This still isn't as useful as it should be by default; it needs to
be a standalone struct/instance so it can be done before net80211
registration occurs, and it can log per-device items.

But, it's getting there.

- Provide necessary includes, that before came via if.h pollution.
- Remove unnecessary ones.

Sponsored by: Netflix
Sponsored by: Nginx, Inc.

Re-commit this - store the alq payload in network order.

Oops - used the wrong field.

Noticed by: nwhitehorn

Add the thread id to the net80211 alq records.

This will (hopefully) aid in debugging concurrency related issues.

Fix style(9) issues.

Fix up the net80211 alq logging - this commit makes it usable.

* revert a local path change that shouldn't have made it to the commit
* fix some indenting/wrapping

* Fix the ale data copy - i should be copying into the ale data pointer,
not over the ale entry itself.

net80211 alq bugfixes:

* Track number of logged operations
* call alq_post() so things are logged
* network order things

Implement very basic ALQ logging for net80211.

This is destined to be a lightweight and optional set of ALQ
probes for debugging events which are just impossible to debug
with printf/log (eg packet TX/RX handling; AMPDU handling.)

The probes and operations themselves will appear in subsequent
commits.