RDMA/hns: Optimize qp destroy flow

Wrap the duplicate code in hip08 and hip06 qp destruction process as
hns_roce_qp_destroy() to simply the qp destroy flow.

Link: https://lore.kernel.org/r/1582526258-13825-2-git-send-email-liweihang@huawei.com


Signed-off-by: Xi Wang <wangxi11@huawei.com>
Signed-off-by: Weihang Li <liweihang@huawei.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>