can: peak_canfd: fix uninitialized symbol warnings

This patch fixes two uninitialized symbol warnings in the new code adding
support of the PEAK-System PCAN-PCI Express FD boards, in the socket-CAN
network protocol family.

Signed-off-by: Stephane Grosjean <s.grosjean@peak-system.com>
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>