can: c_can: remove struct c_can_priv::priv field

It references the clock but it is never used. So let's remove it.

Link: https://lore.kernel.org/r/20210807130800.5246-2-dariobin@libero.it


Signed-off-by: Dario Binacchi <dariobin@libero.it>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>