USB: serial: kl5kusb105: simplify line-status handling

Now that the driver is using usb_control_msg_recv(), the line status
handling can be simplified further by reading directly into the status
variable and doing the endian conversion in place.

Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Johan Hovold <johan@kernel.org>