Btrfs: fix incorrect freeing in scrub_stripe

The address that should be freed is not 'ppath' but 'path'.
Signed-off-by: Tsutomu Itoh <t-itoh@jp.fujitsu.com>
Reviewed-by: Miao Xie <miaoxie@huawei.com>
Signed-off-by: Chris Mason <clm@fb.com>

fs/btrfs/scrub.c

@@ -3053,7 +3053,7 @@ static noinline_for_stack int scrub_stripe(struct scrub_ctx *sctx,
 
 	ppath = btrfs_alloc_path();
 	if (!ppath) {
-		btrfs_free_path(ppath);
+		btrfs_free_path(path);
 		return -ENOMEM;
 	}