MAINTAINERS: update SEC2 driver maintainers list

Adding Kai Ye as SEC2 maintainer.

Signed-off-by: Kai Ye <yekai13@huawei.com>
Signed-off-by: Zaibo Xu <xuzaibo@huawei.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>