TOMOYO: Pass "struct list_head" rather than "void *".

Pass "struct list_head" to tomoyo_add_to_gc() and bring
list_del_rcu() to tomoyo_add_to_gc().

Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Signed-off-by: James Morris <jmorris@namei.org>