RDMA/hns: Fix misplaced call to hns_roce_cleanup_hem_table

The mtt_table is cleaned up during the err_unmap_cqe label, it is a
mistake to duplicate the cleanup during the later unwind labels.

Signed-off-by: Lijun Ou <oulijun@huawei.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>