can: bcm: initialize ifindex for timeouts without previous frame reception

Set in the rx_ifindex to pass the correct interface index in the case of a
message timeout detection. Usually the rx_ifindex value is set at receive
time. But when no CAN frame has been received the RX_TIMEOUT notification
did not contain a valid value.

Cc: linux-stable <stable@vger.kernel.org>
Reported-by: Andre Naujoks <nautsch2@googlemail.com>
Signed-off-by: Oliver Hartkopp <socketcan@hartkopp.net>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>