PCI: fix __must_check warnings

Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/drivers/pci/pci-driver.c b/drivers/pci/pci-driver.c
index d8ace1f..309629e 100644
--- a/drivers/pci/pci-driver.c
+++ b/drivers/pci/pci-driver.c
@@ -56,6 +56,7 @@
 		subdevice=PCI_ANY_ID, class=0, class_mask=0;
 	unsigned long driver_data=0;
 	int fields=0;
+	int retval = 0;
 
 	fields = sscanf(buf, "%x %x %x %x %x %x %lux",
 			&vendor, &device, &subvendor, &subdevice,
@@ -82,10 +83,12 @@
 	spin_unlock(&pdrv->dynids.lock);
 
 	if (get_driver(&pdrv->driver)) {
-		driver_attach(&pdrv->driver);
+		retval = driver_attach(&pdrv->driver);
 		put_driver(&pdrv->driver);
 	}
 
+	if (retval)
+		return retval;
 	return count;
 }
 static DRIVER_ATTR(new_id, S_IWUSR, NULL, store_new_id);