KVM: MMU: using kvm_set_pfn_accessed() instead of mark_page_accessed()

It's a small cleanup that using using kvm_set_pfn_accessed() instead
of mark_page_accessed()

Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index 82f7622..e430a38 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -309,7 +309,7 @@
 	else {
 		old_spte = __xchg_spte(sptep, new_spte);
 		if (old_spte & shadow_accessed_mask)
-			mark_page_accessed(pfn_to_page(spte_to_pfn(old_spte)));
+			kvm_set_pfn_accessed(spte_to_pfn(old_spte));
 	}
 }