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spdx: The BSD-2-Clause-FreeBSD identifier is obsolete, drop -FreeBSD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

Mechanically convert atse(4) to IfAPI

Reviewed by: zlei
Sponsored by: Juniper Networks, Inc.
Differential Revision: https://reviews.freebsd.org/D37795

altera drivers: Remove unused devclass arguments to DRIVER_MODULE.

altera: clean up empty lines in .c and .h files

Convert atse(4) driver for Altera Triple-Speed Ethernet MegaCore to use
xdma(4) interface.

This allows us to switch between Altera mSGDMA or SoftDMA engines used by
atse(4) device.

This also makes atse(4) driver become 25% smaller.

Sponsored by: DARPA, AFRL
Differential Revision: https://reviews.freebsd.org/D9618

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.

MFP4: 221483, 221567, 221568, 221670, 221677, 221678, 221800, 221801,
221804, 221805, 222004, 222006, 222055, 222820, 1135077, 1135118, 1136259

Add atse(4), a driver for the Altera Triple Speed Ethernet MegaCore.

The current driver support gigabit Ethernet speeds only and works with
the MegaCore only in the internal FIFO configuration in the soon to be
open sourced BERI CPU configuration.

Submitted by: bz
MFC after: 3 days
Sponsored by: DARPA/AFRL