RDMA/hns: optimize the duplicated code for qpc setting flow

Currently, more than 20 lines of duplicate code exist in function
'modify_qp_init_to_init' and function 'modify_qp_reset_to_init', which
affects the readability of the code. Consolidate them.

Link: https://lore.kernel.org/r/1562593285-8037-6-git-send-email-oulijun@huawei.com


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