drm/tinydrm: new driver for ILI9341 display panels

This adds a new driver for display panels that use the Ilitek ILI9341
controller. It currently supports a single display panel, namely
the YX240QV29-T (e.g. Adafruit 2.4" TFT).

The init sequence is from the Adafruit Python library for the ILI9341
controller. https://github.com/adafruit/Adafruit_Python_ILI9341

Signed-off-by: David Lechner <david@lechnology.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Reviewed-by: Noralf Trønnes <noralf@tronnes.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20180525193623.15533-5-david@lechnology.com