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/mthca/mthca_provider.c

@@ -1338,7 +1338,7 @@ int mthca_register_device(struct mthca_dev *dev)
 
 	rdma_set_device_sysfs_group(&dev->ib_dev, &mthca_attr_group);
 	dev->ib_dev.driver_id = RDMA_DRIVER_MTHCA;
-	ret = ib_register_device(&dev->ib_dev, "mthca%d", NULL);
+	ret = ib_register_device(&dev->ib_dev, "mthca%d");
 	if (ret)
 		return ret;