netfilter: x_tables: Call xt_init() early when CONFIG_INITCALL_ASYNC=y

classify_tg_init() depends on xt_init() to init xt.
But classify_tg_init() and xt_init() are both in the same
module_init level.

Fix this by moving xt_init() to the rootfs_initcall level.

Change-Id: If9aaae57704e064b719731efa3112d4e652f0069
Signed-off-by: Tao Huang <huangtao@rock-chips.com>

net/netfilter/x_tables.c

@@ -2012,6 +2012,10 @@ static void __exit xt_fini(void)
 	kfree(xt);
 }
 
+#ifdef CONFIG_INITCALL_ASYNC
+rootfs_initcall(xt_init);
+#else
 module_init(xt_init);
+#endif
 module_exit(xt_fini);