ubifs: Fix WARN_ON logic in exit path

ubifs_assert() is not WARN_ON(), so we have to invert
the checks.
Randy faced this warning with UBIFS being a module, since
most users use UBIFS as builtin because UBIFS is the rootfs
nobody noticed so far. :-(
Including me.
Reported-by: Randy Dunlap <rdunlap@infradead.org>
Fixes: 54169ddd ("ubifs: Turn two ubifs_assert() into a WARN_ON()")
Signed-off-by: Richard Weinberger <richard@nod.at>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

fs/ubifs/super.c

@@ -2337,8 +2337,8 @@ late_initcall(ubifs_init);
 
 static void __exit ubifs_exit(void)
 {
-	WARN_ON(list_empty(&ubifs_infos));
-	WARN_ON(atomic_long_read(&ubifs_clean_zn_cnt) == 0);
+	WARN_ON(!list_empty(&ubifs_infos));
+	WARN_ON(atomic_long_read(&ubifs_clean_zn_cnt) != 0);
 
 	dbg_debugfs_exit();
 	ubifs_compressors_exit();