LSM: Convert security_initcall() into DEFINE_LSM()

Instead of using argument-based initializers, switch to defining the
contents of struct lsm_info on a per-LSM basis. This also drops
the final use of the now inaccurate "initcall" naming.

Signed-off-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Casey Schaufler <casey@schaufler-ca.com>
Reviewed-by: James Morris <james.morris@microsoft.com>
Signed-off-by: James Morris <james.morris@microsoft.com>