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spdx: The BSD-2-Clause-FreeBSD identifier is obsolete, drop -FreeBSD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

Regularize my copyright notice

o Remove All Rights Reserved from my notices
o imp@FreeBSD.org everywhere
o regularize punctiation, eliminate date ranges
o Make sure that it's clear that I don't claim All Rights reserved by listing
All Rights Reserved on same line as other copyright holders (but not
me). Other such holders are also listed last where it's clear.

Remove 'All Rights Reserved.' from all of my Copyrights in sys/arm and
always use 'M. Warner Losh' for consistency.

'All Rights Reserved.' was prescribed by the Buenos Aires Copyright
Convention of 1910, but has been mostly dead since the early 1990's
and completely meaningless since 2000 when Nicaragua ratified the
Berne convention.

Some files not done due to ambiguity of various types.

sys/arm: 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.

ARM: Fix ATAG handling in LINUX_BOOT_API:
- Don't convert atags address passed from U-Boot. It's real physical
address (and we have 1:1 mapping).
- Size of tags is encoded in words, not in bytes

ARM: Remove trailing whitespace from sys/arm/include
No functional changes.

Approved by: kib (mentor)

Defines for parsing linux ATAGs lists.