IB/hns: Delete the redundant memset operation

It deleted the redundant memset operation because the memory allocated
by ib_alloc_device has been set zero.

Signed-off-by: Wei Hu (Xavier) <xavier.huwei@huawei.com>
Signed-off-by: Salil Mehta <salil.mehta@huawei.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>