implement the optional byte swap operations with the dedicated
aarch64 instructions.
Signed-off-by: NClaudio Fontana <claudio.fontana@huawei.com>
Reviewed-by: NRichard Henderson <rth@twiddle.net>
Message-id: 51AC9A33.9050003@huawei.com
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>