Add Adafruit pitft35 touchscreen support (#1657)

The dts comes from the Adafruit repository

  https://github.com/adafruit/Adafruit-Pi-Kernel-o-Matic/blob/pitft/pitft35r-overlay.dts



Reformatted slightly to match conventions in the pitft28-resistive-overlay.

Signed-off-by: Scott Ellis <scott@jumpnowtek.com>