MFC r309531,r309553,r309604:

r309531:
Implement fake pmap_mapdev_attr() for ARMv6. This function is referenced,
but never called from DRM2 code. Also, real behavior of pmap_mapdev_attr()
in ARM world is unclear as we don't have any additional attribute for a
device memory type.
r309553:
Fix build breakage caused by r309531.
r309604:
Fix the armv6 build after r309553.

Revert r330897:

This was intended to be a non-functional change. It wasn't. The commit
message was thus wrong. In addition it broke arm, and merged crypto
related code.

Revert with prejudice.

This revert skips files touched in r316370 since that commit was since
MFCed. This revert also skips files that require $FreeBSD$ property
changes.

Thank you to those who helped me get out of this mess including but not
limited to gonzo, kevans, rgrimes.

Requested by: gjb (re)

Partial merge of the SPDX changes

These changes are incomplete but are making it difficult
to determine what other changes can/should be merged.

No objections from: pfg

Copy head@r302406 to stable/11 as part of the 11.0-RELEASE cycle.
Prune svn:mergeinfo from the new branch, as nothing has been merged
here.

Additional commits post-branch will follow.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Include machine/acle-compat.h in cdefs.h on arm if the compiler doesn't
have ACLE support built in. The ACLE (ARM C Language Extensions) defines
a set of standardized symbols which indicate the architecture version and
features available. ACLE support is built in to modern compilers (both
clang and gcc), but absent from gcc prior to 4.4.

ARM (the company) provides the acle-compat.h header file to define the
right symbols for older versions of gcc. Basically, acle-compat.h does
for arm about the same thing cdefs.h does for freebsd: defines
standardized macros that work no matter which compiler you use. If ARM
hadn't provided this file we would have ended up with a big #ifdef __arm__
section in cdefs.h with our own compatibility shims.

Remove #include <machine/acle-compat.h> from the zillion other places (an
ever-growing list) that it appears. Since style(9) requires sys/types.h
or sys/param.h early in the include list, and both of those lead to
including cdefs.h, only a couple special cases still need to include
acle-compat.h directly.

Loves it: imp

Move common definitions from both pmap-v4.h and pmap-v6.h into pmap.h.
(1) MI interface needed for vm subsystem.
(2) MD interface created for ARM architecture to be used in files
shared by armv4 and armv6 platforms.

Rename pmap.h to pmap-v4.h and remove pmap-v6.h include from it.
Create new pmap.h which includes specific header according to
__ARM_ARCH.

Note that <machine/pmap.h> is included from <vm/pmap.h> so one common
<machine/pmap.h> must exist.