FreeBSD on ThunderX2 update

[Jayachandran C.]

Another set of changes needed for ThunderX2 support has been committed
over the past few weeks (thanks andrew@ for fixes and reviews). The
change were to: add IORT table support (r343853, r343856, r343860),
fix a crash seen with INVARIANTS off (r343875, r343876), and handle
more memory regions from the firmware (r343764).

Also, Cavium has released a firmware update at support.cavium.com (for
Sabre reference platforms) that fixes the SATA controller
initialization issue. With all these, the 13-CURRENT should boot and
run fine on ThunderX2 - you just need to add 'options NUMA' to the
conf.

A backport of the needed changes to 12-STABLE is available at:
https://github.com/jchandra-cavm/freebsd/commits/stable/12-tx2 . I
have been running this on my Sabre, and so far it has been stable
under stress. If you have access to a ThunderX2 board, let me know if
it works for you.

Thanks,
JC