uml: fix incompatible types warning in previous SG fix

Fix an incompatible-pointer warning.
Signed-off-by: WANG Cong <xiyou.wangcong@gmail.com>
Signed-off-by: Jeff Dike <jdike@linux.intel.com>
Cc: Jens Axboe <jens.axboe@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

arch/um/drivers/ubd_kern.c

@@ -705,7 +705,7 @@ static int ubd_add(int n, char **error_out)
 	ubd_dev->size = ROUND_BLOCK(ubd_dev->size);
 
 	INIT_LIST_HEAD(&ubd_dev->restart);
-	sg_init_table(&ubd_dev->sg, MAX_SG);
+	sg_init_table(ubd_dev->sg, MAX_SG);
 
 	err = -ENOMEM;
 	ubd_dev->queue = blk_init_queue(do_ubd_request, &ubd_dev->lock);