RDMA/hns: Remove redundant type cast for general pointers

There is no need to do a type cast on genernal pointers, they could be
assigned to any type of variables. In addition, optimize initialization of
some variables and adjust order of them.

Link: https://lore.kernel.org/r/1590152579-32364-2-git-send-email-liweihang@huawei.com


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