IPoIB/cm: Reduce connected mode TX object size

Since IPoIB connected mode does not NETIF_F_SG, we only have one DMA
mapping per send, so we don't need a mapping[] array.  Define a new
struct with a single u64 mapping member and use it for the CM tx_ring.

Signed-off-by: Eli Cohen <eli@mellanox.co.il>
Signed-off-by: Roland Dreier <rolandd@cisco.com>
diff --git a/drivers/infiniband/ulp/ipoib/ipoib.h b/drivers/infiniband/ulp/ipoib/ipoib.h
index a89b9fb..0281c8f 100644
--- a/drivers/infiniband/ulp/ipoib/ipoib.h
+++ b/drivers/infiniband/ulp/ipoib/ipoib.h
@@ -157,6 +157,11 @@
 	u64		mapping[MAX_SKB_FRAGS + 1];
 };
 
+struct ipoib_cm_tx_buf {
+	struct sk_buff *skb;
+	u64		mapping;
+};
+
 struct ib_cm_id;
 
 struct ipoib_cm_data {
@@ -215,7 +220,7 @@
 	struct net_device   *dev;
 	struct ipoib_neigh  *neigh;
 	struct ipoib_path   *path;
-	struct ipoib_tx_buf *tx_ring;
+	struct ipoib_cm_tx_buf *tx_ring;
 	unsigned	     tx_head;
 	unsigned	     tx_tail;
 	unsigned long	     flags;