can: peak_usb: pcan_usb_get_device_id(): read value only in case of success

In case of error, reading value from response argument is useless.

Link: https://lore.kernel.org/r/20210625130931.27438-2-s.grosjean@peak-system.com


Signed-off-by: Stephane Grosjean <s.grosjean@peak-system.com>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>