RDMA/rxe: Fix useless copy in send_atomic_ack

In send_atomic_ack() in rxe_resp.c there is code copying ack_pkt into the
skb->cb[]. This doesn't do anything useful because the cb[] is not used in
the transmit path by the rxe driver.

Remove this code.

Fixes: 4c93496 ("IB/rxe: do not copy extra stack memory to skb")
Link: https://lore.kernel.org/r/20210618045742.204195-2-rpearsonhpe@gmail.com
Signed-off-by: Bob Pearson <rpearson@hpe.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>

drivers/infiniband/sw/rxe/rxe_resp.c

@@ -1023,10 +1023,6 @@ static int send_atomic_ack(struct rxe_qp *qp, struct rxe_pkt_info *pkt,
 	free_rd_atomic_resource(qp, res);
 	rxe_advance_resp_resource(qp);
 
-	memcpy(SKB_TO_PKT(skb), &ack_pkt, sizeof(ack_pkt));
-	memset((unsigned char *)SKB_TO_PKT(skb) + sizeof(ack_pkt), 0,
-	       sizeof(skb->cb) - sizeof(ack_pkt));
-
 	skb_get(skb);
 	res->type = RXE_ATOMIC_MASK;
 	res->atomic.skb = skb;