x86: fill pv_cpu_ops structure with cr8 fields

This patch fills in the read and write cr8 fields with their
native version.

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>