kernel/module.c: fix an unused goto label

Impact: cleanup

Label 'free_init' is only used when defined(CONFIG_MODULE_UNLOAD) &&
defined(CONFIG_SMP), so move it inside to shut up gcc.

Signed-off-by: WANG Cong <xiyou.wangcong@gmail.com>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>