loop: don't increment p->offset with (size_t) -EINVAL

Upon a 'transfer error block' size is set to -EINVAL, but this becomes positive
since size is unsigned: p->offset still gets incremented.
Signed-off-by: Roel Kluin <roel.kluin@gmail.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

drivers/block/loop.c

@@ -392,8 +392,7 @@ lo_splice_actor(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
 	struct loop_device *lo = p->lo;
 	struct page *page = buf->page;
 	sector_t IV;
-	size_t size;
-	int ret;
+	int size, ret;
 
 	ret = buf->ops->confirm(pipe, buf);
 	if (unlikely(ret))