Decode and print the ID_AA64* registers on boot. These registers hold
information on what the core supports. In most cases these will be
identical across most CPUs in the SoC, however there may be the case where,
with a big.LITTLE setup they may differ. In this case we print the
decoded data on all CPUs.

Reviewed by: kib
Sponsored by: ABT Systems Ltd
Differential Revision: https://reviews.freebsd.org/D4725