Add accelerated AES with using the ARMv8 crypto instructions. This is based
on the AES-NI code, and modified as needed for use on ARMv8. When loaded
the driver will check the appropriate field in the id_aa64isar0_el1
register to see if AES is supported, and if so the probe function will
signal the driver should attach.

With this I have seen up to 2000Mb/s from the cryptotest test with a single
thread on a ThunderX Pass 2.0.

Reviewed by: imp
Obtained from: ABT Systems Ltd
MFC after: 1 week
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D8297