Remove sys/mips as the next step of decomissioning mips from the tree.
Remove mips special cases from the kernel make files. Remove the mips
specific linker scripts.

Sponsored by:		Netflix

Move the common kernel function signatures from machine/reg.h to a new
sys/reg.h. This is in preperation for adding PT_GETREGSET to ptrace(2).

Reviewed by:	imp, markj
Sponsored by:	DARPA, AFRL (original work)
Sponsored by:	The FreeBSD Foundation
Differential Revision:	https://reviews.freebsd.org/D19830

The log for the failure contained errors like this:

| In file included from ${SRCTOP}/sys/mips/nlm/dev/net/xlpge.c:34:
| In file included from ${SRCTOP}/sys/sys/systm.h:44:
| In file included from ./machine/atomic.h:849:
| ${SRCTOP}/sys/sys/_atomic_subword.h:222:37: error: unknown type name 'u_long'; did you mean 'long'?
| atomic_testandset_acq_long(volatile u_long *p, u_int v)
|                                     ^~~~~~
|                                     long

And similar "unknown type name" errors for u_int, not recognizing bool as a type, etc.

This was caused by including <sys/param.h> too far down; move it up where it belongs.

While here, add a blank line after '__FBSDID()', in keeping with convention.

Reviewed by:	emaste
Sponsored by:	Panasas
Differential Revision:	https://reviews.freebsd.org/D24242

r357614 added CTLFLAG_NEEDGIANT to make it easier to find nodes that are
still not MPSAFE (or already are but aren’t properly marked).
Use it in preparation for a general review of all nodes.

This is non-functional change that adds annotations to SYSCTL_NODE and
SYSCTL_PROC nodes using one of the soon-to-be-required flags.

Mark all obvious cases as MPSAFE.  All entries that haven't been marked
as MPSAFE before are by default marked as NEEDGIANT

Approved by:	kib (mentor, blanket)
Commented by:	kib, gallatin, melifaro
Differential Revision:	https://reviews.freebsd.org/D23718

switch over to opt-in instead of opt-out for epoch.

Instead of IFF_NEEDSEPOCH, provide IFF_KNOWSEPOCH. If driver marks
itself with IFF_KNOWSEPOCH, then ether_input() would not enter epoch
when processing its packets.

Now this will create recursive entrance in epoch in >90% network
drivers, but will guarantee safeness of the transition.

Mark several tested drivers as IFF_KNOWSEPOCH.

Reviewed by:		hselasky, jeff, bz, gallatin
Differential Revision:	https://reviews.freebsd.org/D23674

supposedly may call into ether_input() without network epoch.

They all need to be reviewed before 13.0-RELEASE.  Some may need
be fixed.  The flag is not planned to be used in the kernel for
a long time.

Reviewed by:	imp
Differential Revision:	https://reviews.freebsd.org/D22032

This fixes an error with modern ld.bfd and is inline with the changes in
r215251 and r217612.

Reviewed by:	imp
Differential Revision:	https://reviews.freebsd.org/D22031

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.