crypto: hisilicon/sec2 - clear SEC debug regs

SEC debug registers aren't cleared even if its driver is removed,
so add a clearing operation in driver removing.

Signed-off-by: Kai Ye <yekai13@huawei.com>
Reviewed-by: Longfang Liu <liulongfang@huawei.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>