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spdx: The BSD-2-Clause-FreeBSD identifier is obsolete, drop -FreeBSD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

[etherswitch] enable phy4/mac4 of ip175c

If MII1 interface is disabled, then enable phy4/mac4.

Submitted by: Hiroki Mori <yamori813@yahoo.co.jp>
Reviewed by: mizhka, adrian
Approved by: adrian (mentor)
Differential Revision: https://reviews.freebsd.org/D6832

Bring in a basic ethernet switch driver for the IP17x series of
switches.

These are notably found on some AR71xx based Mikrotik boards.

Submitted by: Luiz Otavio O Souza <loos.br@gmail.com>
Reviewed by: ray