Input: ipaq-micro-ts - introduce open/close

Wire up open/close so we do not try to send events until someone uses them;
this also allows us to remove micro_ts_remove() and rely fully on managed
resources.

Acked-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>