RDMA: Rename port_callback to init_port

Most provider routines are callback routines which ib core invokes.
_callback suffix doesn't convey information about when such callback is
invoked. Therefore, rename port_callback to init_port.

Additionally, store the init_port function pointer in ib_device_ops, so
that it can be accessed in subsequent patches when binding rdma device to
net namespace.

Signed-off-by: Parav Pandit <parav@mellanox.com>
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>

drivers/infiniband/hw/usnic/usnic_ib_main.c

@@ -422,7 +422,7 @@ static void *usnic_ib_device_add(struct pci_dev *dev)
 	us_ibdev->ib_dev.driver_id = RDMA_DRIVER_USNIC;
 	rdma_set_device_sysfs_group(&us_ibdev->ib_dev, &usnic_attr_group);
 
-	if (ib_register_device(&us_ibdev->ib_dev, "usnic_%d", NULL))
+	if (ib_register_device(&us_ibdev->ib_dev, "usnic_%d"))
 		goto err_fwd_dealloc;
 
 	usnic_fwd_set_mtu(us_ibdev->ufdev, us_ibdev->netdev->mtu);