Remove $FreeBSD$: one-line .c comment pattern

Remove /^/[*/]\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spdx: The BSD-2-Clause-FreeBSD identifier is obsolete, drop -FreeBSD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

libusb(3): Ignore SIGPIPE when initializing the LibUSB v1.0 API.

The LibUSB v1.0 emulation layer uses pipes internally to signal between
threads. When USB devices are reset, as part of loading firmware, SIGPIPE
may happen, and that is expected and should be ignored.

PR: 261891
MFC after: 1 week
Sponsored by: NVIDIA Networking

Fix for building libusb under Linux.

MFC after: 3 days
Sponsored by: Mellanox Technologies

lib: further adoption of SPDX licensing ID tags.

Mainly focus on files that use BSD 2-Clause license, however the tool I
was using mis-identified 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.

Add some missing definitions to build a working FreeBSD's libusb under Linux.

- Make the FreeBSD's USB library compile under Linux.
- Fix a compile warning where the return value of a call
to a write() function was ignored.
- Remove redundant include files from userland USB header files.
- Add some now needed include files to various C-files.