internal/cpu: detect sha-ni instruction support for AMD64
addresses proposal #53084
required by sha-256 change list developed for #50543
Change-Id: I5454d746fce069a7a4993d70dc5b0a5544f8eeaf
Reviewed-on: https://go-review.googlesource.com/c/go/+/408794
Run-TryBot: Keith Randall <khr@golang.org> Reviewed-by: Martin Möhrmann <moehrmann@google.com> Reviewed-by: Keith Randall <khr@golang.org> Reviewed-by: Keith Randall <khr@google.com>
Run-TryBot: Keith Randall <khr@google.com>