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/amso1100/c2_provider.c

@@ -99,14 +99,6 @@ static int c2_query_port(struct ib_device *ibdev,
 	return 0;
 }
 
-static int c2_modify_port(struct ib_device *ibdev,
-			  u8 port, int port_modify_mask,
-			  struct ib_port_modify *props)
-{
-	pr_debug("%s:%u\n", __func__, __LINE__);
-	return 0;
-}
-
 static int c2_query_pkey(struct ib_device *ibdev,
 			 u8 port, u16 index, u16 * pkey)
 {
@@ -817,7 +809,6 @@ int c2_register_device(struct c2_dev *dev)
 	dev->ibdev.dma_device = &dev->pcidev->dev;
 	dev->ibdev.query_device = c2_query_device;
 	dev->ibdev.query_port = c2_query_port;
-	dev->ibdev.modify_port = c2_modify_port;
 	dev->ibdev.query_pkey = c2_query_pkey;
 	dev->ibdev.query_gid = c2_query_gid;
 	dev->ibdev.alloc_ucontext = c2_alloc_ucontext;