can: kvaser_usb: Don't send a RESET_CHIP for non-existing channels

Recent Leaf firmware versions (>= 3.1.557) do not allow to send
commands for non-existing channels.  If a command is sent for a
non-existing channel, the firmware crashes.

Reported-by: Christopher Storah <Christopher.Storah@invetech.com.au>
Signed-off-by: Olivier Sobrie <olivier@sobrie.be>
Signed-off-by: Ahmed S. Darwish <ahmed.darwish@valeo.com>
Cc: linux-stable <stable@vger.kernel.org>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>