directly, call the function pointer (*if_input)(ifp, m). The input routine
expects the packet header to be at the head of the packet, and will adjust
as necessary. Privatize the layer 2 input and output routines, allowing
*_ifattach() to set them up as appropriate.
Reorganise the driver some what.
Rename tr_reset() to the more appropriate tr_stop().
Create a common tropic reset routine and use it in the frontends.
Move the code in tr_config() which is only used in the card attachment
routines into a new tr_attach() function.
Take adapter off the ring through tr_shutdown() in a shutdown hook.
This simplifies the bus-specific frontend.