[SELINUX]: security/selinux/hooks.c: Make 4 functions static.

This patch makes four needlessly global functions static.

Signed-off-by: Adrian Bunk <bunk@stusta.de>
Acked-by: James Morris <jmorris@namei.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: David S. Miller <davem@davemloft.net>