MAINTAINERS: Add Xiu and myself as Lockdown maintainers

The Lockdown LSM has been unmaintained for some time now. It requires
some work to ensure it works as intended.

Xiu Jianfeng and I volunteer to maintain the LSM.

Signed-off-by: Nicolas Bouchinet <nicolas.bouchinet@ssi.gouv.fr>
Acked-by: Xiu Jianfeng <xiujianfeng@huawei.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>

Author: nbouchinet-anssi

MAINTAINERS

@@ -14060,8 +14060,10 @@ F:	Documentation/admin-guide/LSM/LoadPin.rst
 F:	security/loadpin/
 
 LOCKDOWN SECURITY MODULE
+M:	Nicolas Bouchinet <nicolas.bouchinet@oss.cyber.gouv.fr>
+M:	Xiu Jianfeng <xiujianfeng@huawei.com>
 L:	linux-security-module@vger.kernel.org
-S:	Odd Fixes
+S:	Maintained
 T:	git https://git.kernel.org/pub/scm/linux/kernel/git/pcmoore/lsm.git
 F:	security/lockdown/