Add byteorder.S for ARM64

Change-Id: I346e83683ad2318948914c5027123f84d4038451
Reviewed-on: https://review.haiku-os.org/c/haiku/+/3737
Reviewed-by: Fredrik Holmqvist <fredrik.holmqvist@gmail.com>
Reviewed-by: Adrien Destugues <pulkomandy@gmail.com>