Btrfs: Break loop when reach BTRFS_MAX_MIRRORS in scrub_setup_recheck_block()

Use break instead of useless loop should be more suitable in this
case.
Signed-off-by: Zhao Lei <zhaolei@cn.fujitsu.com>
Signed-off-by: Miao Xie <miaox@cn.fujitsu.com>
Signed-off-by: Chris Mason <clm@fb.com>

fs/btrfs/scrub.c

@@ -1394,7 +1394,7 @@ static int scrub_setup_recheck_block(struct scrub_ctx *sctx,
 			struct scrub_page *page;
 
 			if (mirror_index >= BTRFS_MAX_MIRRORS)
-				continue;
+				break;
 
 			sblock = sblocks_for_recheck + mirror_index;
 			sblock->sctx = sctx;