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>

arch/x86/kvm/mmu.c

@@ -309,7 +309,7 @@ static void update_spte(u64 *sptep, u64 new_spte)
 	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));
 	}
 }