RDMA/hns: Remove unnecessary kzalloc

For hns_roce_v2_query_qp and hns_roce_v2_modify_qp,
we can use stack memory to create qp context data.
Make the code simpler.

Signed-off-by: Lang Cheng <chenglang@huawei.com>
Link: https://lore.kernel.org/r/1565276034-97329-11-git-send-email-oulijun@huawei.com
Signed-off-by: Doug Ledford <dledford@redhat.com>