can: mcba_usb: fix device disconnect bug

Currently, when you disconnect the device, the driver infinitely
resubmits all URBs, so you see:

Rx URB aborted (-32)

in an infinite loop.

Fix this by catching -EPIPE (what we get in urb->status when the device
disconnects) and not resubmitting.

With this patch, I can plug and unplug many times and the driver
recovers correctly.

Signed-off-by: Martin Kelly <mkelly@xevo.com>
Cc: linux-stable <stable@vger.kernel.org>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>