IPoIB: Remove unused struct ipoib_cm_tx.ibwc member

struct ipoib_cm_tx.ibwc is unused since commit 1b524963 ("IPoIB/cm:
Use common CQ for CM send completions"), so remove it.
Signed-off-by: Eli Cohen <eli@mellanox.co.il>

drivers/infiniband/ulp/ipoib/ipoib.h

@@ -209,7 +209,6 @@ struct ipoib_cm_tx {
 	unsigned	     tx_tail;
 	unsigned long	     flags;
 	u32		     mtu;
-	struct ib_wc	     ibwc[IPOIB_NUM_WC];
 };
 
 struct ipoib_cm_rx_buf {