Backport of r338074 - generalize uart_bus_probe and add SNPS support to x86

Submitted by: Rajesh Kumar
Differential Revision: https://reviews.freebsd.org/D17381

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

Use the UART frequency when programming the UART clock.

This allows the 16550 support to work correctly on the upcoming
AR934x support.

Preparation work for supporting the AR91xx and AR724x.

* Implement a SoC probe function, from Linux, which determines the
SoC family, type and revision. This only probes the AR71xx series
SoC and (currently) panics on others.

* Migrate some of the AR71XX specific hardware init (USB device, determining
system frequencies) into using the cpuops introduced in an earlier commit.
Other SoC specific hardware stuff (per-device flush/WB, GPIO pin wiring,
Ethernet PLL setup, other things I've likely missed) will be introduced in
subsequent commits.

Reviewed by: imp@
Obtained from: (partially) Linux

Set the svn:eol-style = native and svn:mime-type = text/plain
properties on all files in this tree.

Submitted by: rpaulo@

Place proper svn:keywords tag on all these files. They were created
somehow without them on projects/mips, and that mistake was propigated
over to head.

Submitted by: rpaulo@

Merge from projects/mips to head by hand:

Merge support files for the Atheros AR71xx (and soon AR9xxx)
processors, except files from sys/conf and sys/mips/conf. This work
was done primarily by Olecksandr Tymoshenko and works on the
RouterStation and RouterStation PRO. Other AR71xx-based boards have
been reported as working as well (RouterBoard, for example).

- Move CPU/AHB frequency calculations to functions to
prevent code duplication

- Calculate clock frequency using PLL registers

- Rollback to the hack with 3-bytes offset in base address.
uart_bus_XXXXX resources are handled in uart(4) code
and we need more sophysticated way to define which space
should be used for device based on hints

- Revert changes accidentally killed by merge operation

- Add newbus uart driver implementation