USB: io_ti: fix get_icount for two port adapters

commit 5492bf3d5655b4954164f69c02955a7fca267611 upstream.

Add missing get_icount field to two-port driver.

The two-port driver was not updated when switching to the new icount
interface in commit 0bca1b913aff ("tty: Convert the USB drivers to the
new icount interface").

Signed-off-by: Johan Hovold <jhovold@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>