lockdown: Make lockdown_lsmid static

Fix sparse warning:

security/lockdown/lockdown.c:79:21: warning:
 symbol 'lockdown_lsmid' was not declared. Should it be static?
Signed-off-by: Yue Haibing <yuehaibing@huawei.com>
Reviewed-by: Kees Cook <kees@kernel.org>
Signed-off-by: Paul Moore <paul@paul-moore.com>

security/lockdown/lockdown.c

@@ -76,7 +76,7 @@ static struct security_hook_list lockdown_hooks[] __ro_after_init = {
 	LSM_HOOK_INIT(locked_down, lockdown_is_locked_down),
 };
 
-const struct lsm_id lockdown_lsmid = {
+static const struct lsm_id lockdown_lsmid = {
 	.name = "lockdown",
 	.id = LSM_ID_LOCKDOWN,
 };