TOMOYO: Use common code for open and mkdir etc.

tomoyo_file_perm() and tomoyo_path_permission() are similar.
We can embed tomoyo_file_perm() into tomoyo_path_permission().

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