Encapsulate the qp param setup related code into set_qp_param().

Link: https://lore.kernel.org/r/1582526258-13825-6-git-send-email-liweihang@huawei.comSigned-off-by: NXi Wang <wangxi11@huawei.com>
Signed-off-by: NWeihang Li <liweihang@huawei.com>
Signed-off-by: NJason Gunthorpe <jgg@mellanox.com>