IB/ipath: Fix maximum MTU reporting

Although our chip supports 4K MTUs, our driver doesn't yet support
this feature, so limit the maximum MTU to 2K until we get support for
4K MTUs implemented.

Signed-off-by: Robert Walsh <robert.walsh@qlogic.com>
Signed-off-by: Roland Dreier <rolandd@cisco.com>
diff --git a/drivers/infiniband/hw/ipath/ipath_qp.c b/drivers/infiniband/hw/ipath/ipath_qp.c
index bfef08e..9e07abb 100644
--- a/drivers/infiniband/hw/ipath/ipath_qp.c
+++ b/drivers/infiniband/hw/ipath/ipath_qp.c
@@ -507,8 +507,13 @@
 		    attr->port_num > ibqp->device->phys_port_cnt)
 			goto inval;
 
+	/*
+	 * Note: the chips support a maximum MTU of 4096, but the driver
+	 * hasn't implemented this feature yet, so don't allow Path MTU
+	 * values greater than 2048.
+	 */
 	if (attr_mask & IB_QP_PATH_MTU)
-		if (attr->path_mtu > IB_MTU_4096)
+		if (attr->path_mtu > IB_MTU_2048)
 			goto inval;
 
 	if (attr_mask & IB_QP_MAX_DEST_RD_ATOMIC)