Btrfs: fix wrong orphan count of the fs/file tree

If we add a new orphan item, we should increase the atomic counter,
not decrease it. Fix it.
Signed-off-by: Miao Xie <miaox@cn.fujitsu.com>

fs/btrfs/inode.c

@@ -2228,7 +2228,7 @@ int btrfs_orphan_add(struct btrfs_trans_handle *trans, struct inode *inode)
 			insert = 1;
 #endif
 		insert = 1;
-		atomic_dec(&root->orphan_inodes);
+		atomic_inc(&root->orphan_inodes);
 	}
 
 	if (!test_and_set_bit(BTRFS_INODE_ORPHAN_META_RESERVED,