Input: twl4030-pwrbutton - simplify driver using devm_*

Use managed irq resource to simplify the driver.

Signed-off-by: Sebastian Reichel <sre@debian.org>
Reviewed-by: Aaro Koskinen <aaro.koskinen@iki.fi>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>