net/hns3: remove unnecessary branch

net/hns3: remove unnecessary branch

Because the rte layer of DPDK framework has already processed the case
when the idx is zero before calling the '.mac_addr_remove' ops function,
the input parameter named idx can not be zero in the '.mac_addr_remove'
function. This patch removes unnecessary branch process to check whether
input parameter named idx is zero in the '.mac_addr_remove' ops
implementation function named hns3_remove_mac_addr.

Signed-off-by: Lijun Ou <oulijun@huawei.com>
Signed-off-by: Wei Hu (Xavier) <xavier.huwei@huawei.com>