IB: split struct ib_send_wr

This patch split up struct ib_send_wr so that all non-trivial verbs
use their own structure which embedds struct ib_send_wr.  This dramaticly
shrinks the size of a WR for most common operations:

sizeof(struct ib_send_wr) (old):	96

sizeof(struct ib_send_wr):		48
sizeof(struct ib_rdma_wr):		64
sizeof(struct ib_atomic_wr):		96
sizeof(struct ib_ud_wr):		88
sizeof(struct ib_fast_reg_wr):		88
sizeof(struct ib_bind_mw_wr):		96
sizeof(struct ib_sig_handover_wr):	80

And with Sagi's pending MR rework the fast registration WR will also be
down to a reasonable size:

sizeof(struct ib_fastreg_wr):		64

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Bart Van Assche <bart.vanassche@sandisk.com> [srp, srpt]
Reviewed-by: Chuck Lever <chuck.lever@oracle.com> [sunrpc]
Tested-by: Haggai Eran <haggaie@mellanox.com>
Tested-by: Sagi Grimberg <sagig@mellanox.com>
Tested-by: Steve Wise <swise@opengridcomputing.com>

drivers/infiniband/ulp/ipoib/ipoib.h

@@ -360,7 +360,7 @@ struct ipoib_dev_priv {
 	unsigned	     tx_head;
 	unsigned	     tx_tail;
 	struct ib_sge	     tx_sge[MAX_SKB_FRAGS + 1];
-	struct ib_send_wr    tx_wr;
+	struct ib_ud_wr      tx_wr;
 	unsigned	     tx_outstanding;
 	struct ib_wc	     send_wc[MAX_SEND_CQE];
 
@@ -527,7 +527,7 @@ static inline void ipoib_build_sge(struct ipoib_dev_priv *priv,
 		priv->tx_sge[i + off].addr = mapping[i + off];
 		priv->tx_sge[i + off].length = skb_frag_size(&frags[i]);
 	}
-	priv->tx_wr.num_sge	     = nr_frags + off;
+	priv->tx_wr.wr.num_sge	     = nr_frags + off;
 }
 
 #ifdef CONFIG_INFINIBAND_IPOIB_DEBUG