USB: serial: ti_usb_3410_5052: switch to 30-second closing wait

Switch to using the system-wide default 30-second closing-wait timeout
instead of the driver specific 40-second timeout.

The timeout can be changed per port using TIOCSSERIAL (setserial) if
needed.

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