power: reset: gpio-poweroff: make sys handler priority configurable

Add a priority property equal to gpio-restart to allow increasing the
priority of the gpio-poweroff handler.

Signed-off-by: Stefan Eichenberger <stefan.eichenberger@toradex.com>
Signed-off-by: Francesco Dolcini <francesco.dolcini@toradex.com>
Link: https://lore.kernel.org/r/20231006130428.11259-5-francesco@dolcini.it


Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>