security: define round_hint_to_min in !CONFIG_SECURITY

Fix the header files to define round_hint_to_min() and to define
mmap_min_addr_handler() in the !CONFIG_SECURITY case.

Built and tested with !CONFIG_SECURITY

Signed-off-by: Eric Paris <eparis@redhat.com>
Signed-off-by: James Morris <jmorris@namei.org>