KVM: fix an if() condition

It might have worked in this case since PT_PRESENT_MASK is 1, but let's
express this correctly.
Signed-off-by: NAdrian Bunk <bunk@stusta.de>
Signed-off-by: NAvi Kivity <avi@qumranet.com>

drivers/kvm/mmu.c

@@ -1408,7 +1408,7 @@ static void audit_mappings_page(struct kvm_vcpu *vcpu, u64 page_pte,
 	for (i = 0; i < PT64_ENT_PER_PAGE; ++i, va += va_delta) {
 		u64 ent = pt[i];
 
-		if (!ent & PT_PRESENT_MASK)
+		if (!(ent & PT_PRESENT_MASK))
 			continue;
 
 		va = canonicalize(va);