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

New pmap implementation for 64-bit PowerPC processors. The main focus of
this change is to improve concurrency:
- Drop global state stored in the shadow overflow page table (and all other
global state)
- Remove all global locks
- Use per-PTE lock bits to allow parallel page insertion
- Reconstruct state when requested for evicted PTEs instead of buffering
it during overflow

This drops total wall time for make buildworld on a 32-thread POWER8 system
by a factor of two and system time by a factor of three, providing performance
20% better than similarly clocked Core i7 Xeons per-core. Performance on
smaller SMP systems, where PMAP lock contention was not as much of an issue,
is nearly unchanged.

Tested on: POWER8, POWER5+, G5 UP, G5 SMP (64-bit and 32-bit kernels)
Merged from: user/nwhitehorn/ppc64-pmap-rework
Looked over by: jhibbits, andreast
MFC after: 3 months
Relnotes: yes
Sponsored by: FreeBSD Foundation

Add POWER CPUs to the kernel's knowledge. This does not imply we currently
actually run on any machines with POWER CPUs but avoids closing that door
unnecessarily.

Approved by: re (kib)

Add an abstraction layer to the 64-bit AIM MMU's page table manipulation
logic to support modifying the page table through a hypervisor. This
uses KOBJ inheritance to provide subclasses of the base 64-bit AIM MMU
class with additional methods for page table manipulation.

Many thanks to Peter Grehan for suggesting this design and implementing
the MMU KOBJ inheritance mechanism.