internal/cpu: add aarch64 support functions

Patch from Andreas Schwab.

Change-Id: Ie5466f7c5b2a681ce090797cc52915d93f508847
Reviewed-on: https://go-review.googlesource.com/c/gofrontend/+/281000
Trust: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Peter Weinberger <pjw@google.com>
1 file changed