can: c_can: Introduce c_can_driver_data structure

We want to have more data than just can_dev_id to be present
in the driver data e.g. TI platforms need RAMINIT register
description. Introduce the c_can_driver_data structure and move
the can_dev_id into it.

Tidy up the way it is used on probe().

Signed-off-by: Roger Quadros <rogerq@ti.com>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>