MFC r326204: Do not bind to CPUs with SMT

Do not bind to CPUs with SMT, which use a different CPU numbering convention
that does not play well with this driver.

MFC r317191, r317195: Don't ignore "disabled" CPUs

r317191 (cognet):
ePAPR states that any non-boot CPU will come in "disabled" state. So we
should not consider a "disabled" cpu as a CPU we have to ignore, and we
should use them if they provide a "enable-method".
While I'm there, support "ok" as well as "okay", while ePAPR only accepts
"okay", linux accepts "ok" too so we can expect it to be used.

r317195 (cognet):
Update comment ot reflect realilty, we know also take care of CPUs that
provide a enable-method.

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

Limit ofw_cpu_early_foreach() to CPUs only

On some platforms, the /cpus node contains cpu-to-cluster
map which deffinitely is not a CPU node. Its presence was
causing incrementing of "id" variable and reporting more
CPUs available than it should.
To make "id" valid, increment it only when an entry really
is a CPU device.

Reviewed by: andrew
Obtained from: Semihalf
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D3216

Adda function to iterate over the cpu nodes in the OFW or FDT data. This
will be used with arm64 to find which cpus to enable, and could also be
used with 32-bit arm and mips for the same purpose.

Differential Revision: https://reviews.freebsd.org/D1825
Sponsored by: The FreeBSD Foundation

Add support to get the cpu ID from its device driver in a generic way.
This will be needed by arm64 to find the value to pass to the psci (Power
State Coordination Interface) driver, among other things, used to enable
cores.

Differential Revision: https://reviews.freebsd.org/D1824
Reviewed by: imp
Sponsored by: The FreeBSD Foundation

Update the parsing of the cpu node. We are unable to use the reg property
as the cpu id on arm64 as it may use two cells. In it's place we can use
the device id.

It is expected we will use the reg data on arm64 to enable cores so we
still need to read and store it even if it is not yet used.

Differential Revision: https://reviews.freebsd.org/D1555
Reviewed by: nwhitehorn
Sponsored by: The FreeBSD Foundation

Make the clock-frequency property optional as it may not be present on FDT
systems.

Sponsored by: The FreeBSD Foundation

Don't assume required FDT properties are present.

Use standard BSD license disclaimer text

Approved by: benno, nwhitehorn

Move ofw_cpu.c to sys/dev/ofw so that it can be used by other
architectures.

Differential Revision: https://reviews.freebsd.org/D1307
Reviewed by: jhibbits

Move Open Firmware device root on PowerPC, ARM, and MIPS systems to
a sub-node of nexus (ofwbus) rather than direct attach under nexus. This
fixes FDT on x86 and will make coexistence with ACPI on ARM systems easier.
SPARC is unchanged.

Reviewed by: imp, ian

Fix error in r252115: space for the softc needs to be allocated. This
seemed to be working by chance on most systems.

Cache the Open Firmware CPU properties at attach time, so we don't always
enter it at runtime to get static data.

- There's no need to overwrite the default device method with the default
one. Interestingly, these are actually the default for quite some time
(bus_generic_driver_added(9) since r52045 and bus_generic_print_child(9)
since r52045) but even recently added device drivers do this unnecessarily.
Discussed with: jhb, marcel
- While at it, use DEVMETHOD_END.
Discussed with: jhb
- Also while at it, use __FBSDID.

Introduce support for cpufreq on PowerPC with the dynamic frequency
switching capabilities of the MPC7447A and MPC7448.