ARM: dts: sun4i: Add touchscreen node to chuwi-v7 dts file

Add a node describing the focaltech ft5306de4 touchscreen found on
chuwi-v7-cw0825 tablets.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>