x86: patching functions on 64-bit

Like i386, x86_64 also need to include its own patching function.
(Well, if you're not in a hurry, and don't care about speed, you don't
really _need_ ;-))

So here they are. Not much different in essence from i386

Signed-off-by: Glauber de Oliveira Costa <gcosta@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>