tomoyo: Use bin2c to generate builtin-policy.h

Simplify the Makefile by using a readily available tool instead of a
custom sed script. The downside is that builtin-policy.h becomes
unreadable for humans, but it is only a generated file.

Acked-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Signed-off-by: Michal Marek <mmarek@suse.cz>