crypto: hisilicon/qm - delete redundant null assignment operations

There is no security data in the pointer. It is only a value transferred
as a structure. It makes no sense to zero a variable that is on the stack.
So not need to set the pointer to null.

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