KVM: MMU: fix release noslot pfn

We can not directly call kvm_release_pfn_clean to release the pfn
since we can meet noslot pfn which is used to cache mmio info into
spte

Signed-off-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Cc: stable@vger.kernel.org
Signed-off-by: Avi Kivity <avi@redhat.com>

arch/x86/kvm/mmu.c

@@ -2497,8 +2497,7 @@ static void mmu_set_spte(struct kvm_vcpu *vcpu, u64 *sptep,
 		}
 	}
 
-	if (!is_error_pfn(pfn))
-		kvm_release_pfn_clean(pfn);
+	kvm_release_pfn_clean(pfn);
 }
 
 static void nonpaging_new_cr3(struct kvm_vcpu *vcpu)