MFC r320065: arm: add .arch_extension sec for smc instruction

Clang 4.0 accepts the smc instruction with or without specifying
.arch_extension sec, but Clang 5.0 produces an error without it.

Sponsored by: The FreeBSD Foundation

MFC r317361:

Call the PSCI reset from cpu_reset on arm64. When rebooting from DDB the
kernel calls this directly so the event handler is not called, meaning
the computer fails to reboot.

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

Start to support PSCI 1.0. For all the functions we currently support this
can be seen as the same as 0.2. There are changes with the data passed to
CPU_SUSPEND, however we don't yet use this call.

Sponsored by: ABT Systems Ltd

Rework the PSCI cpu on code to allow it to work before device drivers have
started. This allows this functions to be used with the regular ARM SMP
initialisation sequence.

Add psci for arm64. This is currently used when rebooting and powering off
in qemu.

Sponsored by: The FreeBSD Foundation

Add a driver for the ARM Power State Coordination Interface (PSCI). This
handles versions 0.1 and 0.2 of the standard on 32-bit ARM.

With this driver we can shutdown in QEMU. Further work is needed to
turn secondary cores on on boot and to support later revisions of the
specification.

Submitted by: Robin Randhawa <Robin.Randhawa at ARM.com>
Sponsored by: The FreeBSD Foundation