We will need helpers that only make sense with AArch64. Add
helper-a64.{c,h} files as stubs that we can fill with these
helpers in the following patches.
Signed-off-by: NAlexander Graf <agraf@suse.de>
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>
Reviewed-by: NRichard Henderson <rth@twiddle.net>