Input: st1232 - switch to gpiod API

Use devm_gpiod_get_optional() and gpiod_set_value_cansleep() instead
of the old API. The st1232_ts_power() now passes on the inverted "poweron"
value to reflect the correct logical value.

Signed-off-by: Martin Kepplinger <martin.kepplinger@ginzinger.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>