ARM: dts: sun8i: Add touchscreen node for sun8i-a23-inet86dz

The inet86dz tablet has a gsl1680 touchscreen,
add a dt node describing it.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Acked-by: Chen-Yu Tsai <wens@csie.org>