RDMA/hns: Create QP with selected QPN for bank load balance

In order to improve performance by balancing the load between different
banks of cache, the QPC cache is desigend to choose one of 8 banks
according to lower 3 bits of QPN. The hns driver needs to count the number
of QP on each bank and then assigns the QP being created to the bank with
the minimum load first.

Link: https://lore.kernel.org/r/1606220649-1465-1-git-send-email-liweihang@huawei.com
Signed-off-by: Yangyang Li <liyangyang20@huawei.com>
Signed-off-by: Weihang Li <liweihang@huawei.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>