sbin: Automated cleanup of cdefs and other formatting

Apply the following automated changes to try to eliminate
no-longer-needed sys/cdefs.h includes as well as now-empty
blank lines in a row.

Remove /^#if.*\n#endif.*\n#include\s+<sys/cdefs.h>.*\n/
Remove /\n+#include\s+<sys/cdefs.h>.*\n+#if.*\n#endif.*\n+/
Remove /\n+#if.*\n#endif.*\n+/
Remove /^#if.*\n#endif.*\n/
Remove /\n+#include\s+<sys/cdefs.h>\n#include\s+<sys/types.h>/
Remove /\n+#include\s+<sys/cdefs.h>\n#include\s+<sys/param.h>/
Remove /\n+#include\s+<sys/cdefs.h>\n#include\s+<sys/capsicum.h>/

Sponsored by: Netflix

Remove $FreeBSD$: one-line .c pattern

Remove /^[\s*]*__FBSDID\("\$FreeBSD\$"\);?\s*\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spdx: The BSD-2-Clause-FreeBSD identifier is obsolete, drop -FreeBSD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

Open device with O_RDONLY when command is non-invasive.

This allows to use some of the subcommands against mounted nvd devices.

MFC after: 1 week
Sponsored by: iXystems, Inc.

Fix various Coverity-detected errors in nvmecontrol

This fixes several Coverity-detected errors in nvmecontrol. While in
here, a couple additional errors with shift/mask confusion that were
not diagnosed by Coverity are also fixed.

CIDs addressed: 1040299, 1040300, 1403972, 1403973, 1403985, 1403988,
1403990, 1404374, 1404427, 1404469, 1404510, 1404534, 1418118

CID 1403657 (resource leak of shared library handle) was marked
"intentional" in the Coverity scan database.

Reviewed by: vangyzen, robert.herndon_dell.com
Reviewed by: daniel.william.ryan_gmail.com (earlier version)
Reviewed by: rramsden_isilon.com (earlier version), imp
MFC after: 5 days
Sponsored by: Dell EMC Isilon
Differential Revision: https://reviews.freebsd.org/D24203

Rename function added in r350523 to make gcc happy.

MFC after: 2 weeks

Add IOCTL to translate nvdX into nvmeY and NSID.

While very useful by itself, it also makes `nvmecontrol` not depend on
hardcoded device names parsing, that in its turn makes simple to take
nvdX (and potentially any other) device names as arguments.

Also added IOCTL bypass from nvdX to respective nvmeYnsZ makes them
interchangeable for management purposes.

MFC after: 2 weeks
Sponsored by: iXsystems, Inc.