can: janz-ican3: remove dead code

The code which used this variable was removed during review, before the
driver was added to mainline Linux. It is now dead code, and can be
removed.

Signed-off-by: Ira W. Snyder <iws@ovro.caltech.edu>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>