nilfs2: fix leak of shadow dat inode in error path of load_nilfs

If load_nilfs() gets an error while doing recovery, it will fail to
free the shadow inode of dat (nilfs->ns_gc_dat).

This fixes the leak issue.

Signed-off-by: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>
diff --git a/fs/nilfs2/the_nilfs.c b/fs/nilfs2/the_nilfs.c
index 4317f17..ba7c10c 100644
--- a/fs/nilfs2/the_nilfs.c
+++ b/fs/nilfs2/the_nilfs.c
@@ -446,6 +446,7 @@
 	nilfs_mdt_destroy(nilfs->ns_cpfile);
 	nilfs_mdt_destroy(nilfs->ns_sufile);
 	nilfs_mdt_destroy(nilfs->ns_dat);
+	nilfs_mdt_destroy(nilfs->ns_gc_dat);
 
  failed:
 	nilfs_clear_recovery_info(&ri);