virtio_blk: Delete an unnecessary initialisation in init_vq()

The local variable "err" will be set to an appropriate value
by a following statement.
Thus omit the explicit initialisation at the beginning.
Signed-off-by: Markus Elfring <elfring@users.sourceforge.net>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

drivers/block/virtio_blk.c

@@ -376,7 +376,7 @@ static void virtblk_config_changed(struct virtio_device *vdev)
 
 static int init_vq(struct virtio_blk *vblk)
 {
-	int err = 0;
+	int err;
 	int i;
 	vq_callback_t **callbacks;
 	const char **names;