device: Add callback for set interface rx-mode

device: Add callback for set interface rx-mode

- When the interface rx-mode is changed via CLI, the corresponding device
may want to know about it and to reset the driver. This patch is to add
the callback.

- In the function vnet_hw_interface_set_rx_mode, it appears it is missing
a line
  hw->rx_mode_by_queue[queue_id] = mode

because the function is checking if the new mode is the same as
hw->rx_mode_by_queue which is initialized to POLLING. So if the function is
called to change the mode to interrupt, it just returns without doing
anything. This is the check that I am talking about in the same function.

  if (hw->rx_mode_by_queue[queue_id] == mode)
    return 0;

Change-Id: Iaca2651c43e0ae3fda6fd8dc128e247b0851cc65
Signed-off-by: Steven <sluong@cisco.com>