ThunderX2 support in FreeBSD/arm64

[Jayachandran C.]

Over the last few weeks I have committed changes for a few outstanding
items needed for ThunderX2 support in FreeBSD/arm64. Most of the
changes were to fix-up support for ACPI based PCI controllers and to
enable ACPI based NUMA (thanks to andrew, markj and jhb for reviews).

With these, 13-CURRENT works well enough for testing - so if you have
access to a ThunderX2, I would like to hear how well it works for you.
Also, the same series added support for running FreeBSD on qemu/kvm on
Linux with ACPI support. You can test the changes (including NUMA) in
a VM if you don't want to do a full install.

Few notes:
- you will need the latest firmware from support.cavium.com, the older
firmware had a bug which resulted in a crash at SATA controller init.
- you will need to enable 'options NUMA' in your conf file (most of
the systems available are multi-socket)
- keep WITNESS & INVARIANTS on
- if you are using qemu, use '-M virt,gic-version=3'  at qemu command
line and pass 'kern.cfg.order=acpi' and 'hw.pci.honor_msi_blacklist=0'
to loader

JC