x86: don't set pagetable_setup_{start,done} hooks on 64-bit

paravirt_pagetable_setup_{start,done}() are not used (yet) under x86_64,
and native_pagetable_setup_{start,done}() don't exist on x86_64. So they
don't need to be set.
Signed-off-by: NEduardo Habkost <ehabkost@redhat.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>

arch/x86/kernel/paravirt.c

@@ -367,8 +367,10 @@ struct pv_apic_ops pv_apic_ops = {
 };
 
 struct pv_mmu_ops pv_mmu_ops = {
+#ifndef CONFIG_X86_64
 	.pagetable_setup_start = native_pagetable_setup_start,
 	.pagetable_setup_done = native_pagetable_setup_done,
+#endif
 
 	.read_cr2 = native_read_cr2,
 	.write_cr2 = native_write_cr2,