can: kvaser_usb: Correct return value in printout

commit 8f65a923e6b628e187d5e791cf49393dd5e8c2f9 upstream.

If the return value from kvaser_usb_send_simple_msg() was non-zero, the
return value from kvaser_usb_flush_queue() was printed in the kernel
warning.

Signed-off-by: Jimmy Assarsson <jimmyassarsson@gmail.com>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>