ilitek: Rename GPIO device tree properties
The ilitek driver uses device tree properties pre-fixed with "ilitek". Although this is a good way to distinguish mainline/standard kernel and vendor specific properties this is in our case not useful.
We already introduces the non-prefixed version with the same information mainly to use the Garz & Fricke specific touchgpio API.
Thus simply re-use the non-prefixed properties to reduce information duplication in the device tree.
This also reduces the complexity in the Garz & Fricke overlay mechanism using gfxml2dto.