flush_comp is initialized when CMD_FLUSH_QUEUE is sent to the device and
completed when the device sends CMD_FLUSH_QUEUE_RESP.

This causes completion of uninitialized completion if the device sends
CMD_FLUSH_QUEUE_RESP before CMD_FLUSH_QUEUE is ever sent (e.g. as a
response to a flush by a previously bound driver, or a misbehaving
device).

Fix that by initializing flush_comp in kvaser_usb_init_one() like the
other completions.

This issue is only triggerable after RX URBs have been set up, i.e. the
interface has been opened at least once.

Cc: stable@vger.kernel.org
Fixes: aec5fb22 ("can: kvaser_usb: Add support for Kvaser USB hydra family")
Tested-by: Jimmy Assarsson <extja@kvaser.com>
Signed-off-by: Anssi Hannula <anssi.hannula@bitwise.fi>
Signed-off-by: Jimmy Assarsson <extja@kvaser.com>
Link: https://lore.kernel.org/all/20221010150829.199676-3-extja@kvaser.comSigned-off-by: Marc Kleine-Budde <mkl@pengutronix.de>