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

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

Fix some common typos in source code comments

- s/struture/structure/
- s/structre/structure/

MFC after: 5 days

Correct typo in ATA_WRITE_UNCORRECTABLE_PSEUDO

Also correct a typo in the comment for these values, noted by jimharris.

Reviewed by: jimharris
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D3715

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.

Add isci(4) driver for amd64 and i386 targets.

The isci driver is for the integrated SAS controller in the Intel C600
(Patsburg) chipset. Source files in sys/dev/isci directory are
FreeBSD-specific, and sys/dev/isci/scil subdirectory contains
an OS-agnostic library (SCIL) published by Intel to control the SAS
controller. This library is used primarily as-is in this driver, with
some post-processing to better integrate into the kernel build
environment.

isci.4 and a README in the sys/dev/isci directory contain a few
additional details.

This driver is only built for amd64 and i386 targets.

Sponsored by: Intel
Reviewed by: scottl
Approved by: scottl