IB/mthca: Safer max_send_sge/max_recv_sge calculation

Calculation of QP capabilities still isn't exactly right in mthca:
max_send_sge/max_recv_sge fields returned in create_qp can exceed the
handware supported limits.
Signed-off-by: Michael S. Tsirkin <mst@mellanox.co.il>
Signed-off-by: Roland Dreier <rolandd@cisco.com>

drivers/infiniband/hw/mthca/mthca_qp.c

@@ -918,10 +918,12 @@ static void mthca_adjust_qp_caps(struct mthca_dev *dev,
         else
 		qp->max_inline_data = max_data_size - MTHCA_INLINE_HEADER_SIZE;
 
-	qp->sq.max_gs = max_data_size / sizeof (struct mthca_data_seg);
-	qp->rq.max_gs = (min(dev->limits.max_desc_sz, 1 << qp->rq.wqe_shift) -
-			sizeof (struct mthca_next_seg)) /
-			sizeof (struct mthca_data_seg);
+	qp->sq.max_gs = min_t(int, dev->limits.max_sg,
+			      max_data_size / sizeof (struct mthca_data_seg));
+	qp->rq.max_gs = min_t(int, dev->limits.max_sg,
+			       (min(dev->limits.max_desc_sz, 1 << qp->rq.wqe_shift) -
+				sizeof (struct mthca_next_seg)) /
+			       sizeof (struct mthca_data_seg));
 }
 
 /*