Zephyr have recently added this device tree entry to provide a common
interface for input handlers.
This means we can remove the overlay required for the i.MX RT1170
shield, and remove our modifications some of our modifications for the
native sim. It also means that we don't have to make device tree
modifications to support other boards in the future.
This gives us access to the new `zephyr,touch` device tree entry,
which will allow us to produce a more generic touch input handler.
INPUT_CALLBACK_DEFINE and the input callback now require `void *`
argument for user data. For now we leave this unused.
When this driver is using the DMA API, we cannot do partial updates.
Previously, this code would then perform a full-screen DMA transfer for
each region the renderer changes. Now we make modifications to the pixel
data of the dirty regions, if required, and then do one fill-scren DMA
transfer of the final render buffer.
