_bus.h: Use standard licnese text

All of these used the 'immediately at beginning' variation of the
BSD-2-Clause license. This wasn't intentional, just what I copied from
from a random file in the tree back in 2005. It was not an intentional
decision.

The different arch bus.h files are a mix of BSD-2-Clause and
BSD-4-Clause that have various copyright holders (Charles M. Hannum,
Christopher G. Demetriou, The NetBSD Foundation and KATO Takenori), and
some of the content of these files were likely copied from there.
However, apart from the uncopyrightable interface lines, there are very
few comments. It's unclear if these comments are 'original material'
here to copyright, but to the extent that there is, license it under the
standard BSD-2-Clause copyright that's the norm for the project today.
In any event, the standard BSD-2-Clause is also closer to those
originals.

In addition, FreeBSD uses different type definitions than the original
NetBSD code in part. The comments that were copied have been copied a
lot, but appear in NetBSD's bus.h files in NetBSD 1.3.

While I'm here, assign the copyright, to the extent any exists from me,
to the FreeBSD Foundation. I just cut and pasted these into _bus.h from
the different machine files and those files have a rich history of
modification from the original imports from NetBSD over more than 25
years so it's tricky to say who, exactly, wrote each bit. Given the size
of the files, this seems like the best compromise. Also add an
acknowledgement to the NetBSD 1.3 bus.h files and their authors (there
were no additional FreeBSD authors listed in the various
sys/*/include/bus.h files). Finally, use the SPDX identifier instead of
multiple copies of the text.

Differential Revision: https://reviews.freebsd.org/D42532
Sponsored by: Netflix

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

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

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.

Bring in the start of the arm64 kernel.

This is only the minimum set of files needed to boot in qemu. As such it is
missing a few things.

The bus_dma code is currently only stub functions with a full implementation
from the development tree to follow.

The gic driver has been copied as the interrupt framework is different. It
is expected the two drivers will be merged by the arm intrng project,
however this will need to be imported into the tree and support for arm64
would need to be added.

This includes code developed by myself, SemiHalf, Ed Maste, and Robin
Randhawa from ARM. This has been funded by the FreeBSD Foundation, with
early development by myself in my spare time with assistance from Robin.

Differential Revision: https://reviews.freebsd.org/D2199
Reviewed by: emaste, imp
Relnotes: yes
Sponsored by: The FreeBSD Foundation