RDMA: Allow for NULL .modify_device() and .modify_port() methods

These methods don't make sense for iWARP devices, so rather than
forcing them to implement stubs, just return -ENOSYS in the core if
the hardware driver doesn't set .modify_device and/or .modify_port.

Signed-off-by: Roland Dreier <roland@purestorage.com>

drivers/infiniband/hw/nes/nes_verbs.c

@@ -604,16 +604,6 @@ static int nes_query_port(struct ib_device *ibdev, u8 port, struct ib_port_attr
 }
 
 
-/**
- * nes_modify_port
- */
-static int nes_modify_port(struct ib_device *ibdev, u8 port,
-		int port_modify_mask, struct ib_port_modify *props)
-{
-	return 0;
-}
-
-
 /**
  * nes_query_pkey
  */
@@ -3882,7 +3872,6 @@ struct nes_ib_device *nes_init_ofa_device(struct net_device *netdev)
 	nesibdev->ibdev.dev.parent = &nesdev->pcidev->dev;
 	nesibdev->ibdev.query_device = nes_query_device;
 	nesibdev->ibdev.query_port = nes_query_port;
-	nesibdev->ibdev.modify_port = nes_modify_port;
 	nesibdev->ibdev.query_pkey = nes_query_pkey;
 	nesibdev->ibdev.query_gid = nes_query_gid;
 	nesibdev->ibdev.alloc_ucontext = nes_alloc_ucontext;