RDMA/iw_cxgb4: Avoid freeing skb twice in arp failure case

_put_ep_safe() and _put_pass_ep_safe() free the skb before it is freed by
process_work(). fix double free by freeing the skb only in process_work().

Fixes: 1dad0eb ("iw_cxgb4: Avoid touch after free error in ARP failure handlers")
Link: https://lore.kernel.org/r/1572006880-5800-1-git-send-email-bharat@chelsio.com
Signed-off-by: Dakshaja Uppalapati <dakshaja@chelsio.com>
Signed-off-by: Potnuri Bharat Teja <bharat@chelsio.com>
Reviewed-by: Jason Gunthorpe <jgg@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>

drivers/infiniband/hw/cxgb4/cm.c

@@ -495,7 +495,6 @@ static int _put_ep_safe(struct c4iw_dev *dev, struct sk_buff *skb)
 
 	ep = *((struct c4iw_ep **)(skb->cb + 2 * sizeof(void *)));
 	release_ep_resources(ep);
-	kfree_skb(skb);
 	return 0;
 }
 
@@ -506,7 +505,6 @@ static int _put_pass_ep_safe(struct c4iw_dev *dev, struct sk_buff *skb)
 	ep = *((struct c4iw_ep **)(skb->cb + 2 * sizeof(void *)));
 	c4iw_put_ep(&ep->parent_ep->com);
 	release_ep_resources(ep);
-	kfree_skb(skb);
 	return 0;
 }