Add DT binding document for the Ilitek ILI210x and ILI251x
touchscreen controllers.
Signed-off-by: NMarek Vasut <marex@denx.de>
Reviewed-by: NRob Herring <robh@kernel.org>
Signed-off-by: NDmitry Torokhov <dmitry.torokhov@gmail.com>