TOMOYO: Extract bitfield

Since list elements are rounded up to kmalloc() size rather than sizeof(int),
saving one byte by using bitfields is no longer helpful.

Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Acked-by: Serge Hallyn <serue@us.ibm.com>
Signed-off-by: James Morris <jmorris@namei.org>