can: kvaser_usb: Fix comparison bug in kvaser_usb_read_bulk_callback()

can: kvaser_usb: Fix comparison bug in kvaser_usb_read_bulk_callback()

commit e84f44eb5523401faeb9cc1c97895b68e3cfb78d upstream.

The conditon in the while-loop becomes true when actual_length is less than
2 (MSG_HEADER_LEN). In best case we end up with a former, already
dispatched msg, that got msg->len greater than actual_length. This will
result in a "Format error" error printout.

Problem seen when unplugging a Kvaser USB device connected to a vbox guest.

warning: comparison between signed and unsigned integer expressions
[-Wsign-compare]

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>