RDMA/hns: Use IDA interface to manage xrcd index

Switch xrcd index allocation and release from hns own bitmap interface
to IDA interface.

Link: https://lore.kernel.org/r/1623325814-55737-7-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>