xen/pciback: double lock typo

We called mutex_lock() twice instead of unlocking.
Signed-off-by: NDan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: NKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>

drivers/xen/xen-pciback/vpci.c

@@ -238,7 +238,7 @@ static int __xen_pcibk_get_pcifront_dev(struct pci_dev *pcidev,
 			}
 		}
 	}
-	mutex_lock(&vpci_dev->lock);
+	mutex_unlock(&vpci_dev->lock);
 	return found;
 }