can: kvaser_usb: fix usb endpoints detection

Some devices, like the Kvaser Memorator Professional, have several bulk in
endpoints. Only the first one found must be used by the driver. The same holds
for the bulk out endpoint. The official Kvaser driver (leaf) was used as
reference for this patch.

Cc: linux-stable <stable@vger.kernel.org>
Signed-off-by: Olivier Sobrie <olivier@sobrie.be>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>