Purge more stray embedded $FreeBSD$ strings

These do not use __FBSDID but instead use bare char arrays.

Reviewed by: imp, emaste
Differential Revision: https://reviews.freebsd.org/D41957

spdx: The BSD-2-Clause-FreeBSD identifier is obsolete, drop -FreeBSD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

various: 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.

Reassign copyright statements on several files from Advanced
Computing Technologies LLC to Hudson River Trading LLC.

Approved by: Hudson River Trading LLC (who owns ACT LLC)
MFC after: 1 week

Align the PCI Express #defines with the style used for the PCI-X
#defines. This also has the advantage that it makes the names more
compact, iand also allows us to correct the non-uniform naming of
the PCIM_LINK_* defines, making them all consistent amongst themselves.

This is a mostly mechanical rename:
s/PCIR_EXPRESS_/PCIER_/g
s/PCIM_EXP_/PCIEM_/g
s/PCIM_LINK_/PCIEM_LINK_/g

When this is MFC'd, #defines will be added for the old names to assist
out-of-tree drivers.

Discussed with: jhb
MFC after: 1 week

- Denote PCI-e endpoints that support FLR.
- Make parsing of PCI-e extended capabilities assume that future version
numbers are backwards compatible.
- Add new AER error descriptions.
- Add descriptions for more PCI-e extended capabilities.

MFC after: 1 week

Add a new -e flag to pciconf(8)'s list mode to display PCI error details.
Currently this dumps the status of any error bits in the PCI status register
and PCI-express device status register. It also lists any errors indicated
by version 1 of PCI-express Advanced Error Reporting (AER).

MFC after: 1 week