KVM: MMU: use kvm_release_pfn_clean to release pfn

The current code depends on the fact that fault_page is the normal page,
however, we will use the error code instead of these dummy pages in the
later patch, so we use kvm_release_pfn_clean to release pfn which will
release the error code properly
Signed-off-by: NXiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Signed-off-by: NAvi Kivity <avi@redhat.com>

arch/x86/kvm/mmu.c

@@ -3275,7 +3275,7 @@ static bool try_async_pf(struct kvm_vcpu *vcpu, bool prefault, gfn_t gfn,
 	if (!async)
 		return false; /* *pfn has correct page already */
 
-	put_page(pfn_to_page(*pfn));
+	kvm_release_pfn_clean(*pfn);
 
 	if (!prefault && can_do_async_pf(vcpu)) {
 		trace_kvm_try_async_get_page(gva, gfn);