RDMA/hns: Refactor the alloc_cqc()

Abstract the alloc_cqc() into several parts and separate the process
unrelated to allocating CQC.

Link: https://lore.kernel.org/r/20220302064830.61706-10-liangwenpeng@huawei.com


Signed-off-by: Wenpeng Liang <liangwenpeng@huawei.com>
Reviewed-by: Leon Romanovsky <leonro@nvidia.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>