RDMA/hns: Remove the unused hns_roce_bitmap_free_range function

hns_roce_bitmap_free_range() is only called inside hns_roce_bitmap_free(),
and the input parameter "cnt" is set to a constant 1. In addition, the
driver does not use alloc_range scenarios, so free_range does not need to
exist.

Link: https://lore.kernel.org/r/1623325814-55737-3-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>