ARM: dts: tps65217: Add power button interrupt to the common tps65217.dtsi file

The interrupt for power button is static data that comes from the
datasheet, there is no reason to need to define this value on every
board so seams reasonable put this information into the common tps65217
file.

Signed-off-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>