RDMA/hns: Remove redundant assignment of wc->smac when polling cq

The field smac in ib_wc was used for create AH and then it will be treated
as destination mac address in UD sqwqe, but related code about filling smac
into AH has been removed in core. Actually, the dmac in UD sqwqe is parsed
from the dgid in grh which is passed in by ULP now, so this assignment
should be removed.

Link: https://lore.kernel.org/r/1584674622-52773-10-git-send-email-liweihang@huawei.com
Signed-off-by: Weihang Li <liweihang@huawei.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>