net: can: esd_usb2: check index of array before accessing

The esd_usb2_read_bulk_callback() function is parsing the data that comes from
the USB CAN adapter. One datum is used as an index to access the dev->nets[]
array. This patch adds the missing bounds checking.

Acked-by: Matthias Fuchs <matthias.fuchs@esd.eu>
Signed-off-by: Maximilian Schneider <max@schneidersoft.net>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>