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>