RDMA/hns: Handling the error return value of hem function

Handling the error return value of hns_roce_calc_hem_mhop.

Signed-off-by: Lang Cheng <chenglang@huawei.com>
Link: https://lore.kernel.org/r/1565276034-97329-8-git-send-email-oulijun@huawei.com


Signed-off-by: Doug Ledford <dledford@redhat.com>