iw_cxgb4: Check for send WR also while posting write with completion WR

Inorder to optimize the NVMEoF read IOPs, iw_cxgb4 posts a FW Write with
Completion WQE that combines an RDMA Write WR and the subsequent RDMA Send
with Invalidate WR.

This patch is an extension to it, where it posts a Write with completion
for RDMA WRITE WR + RDMA SEND WR combination as well.

Reviewed-by: Steve Wise <swise@opengridcomputing.com>
Signed-off-by: Potnuri Bharat Teja <bharat@chelsio.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>