ARM: dts: imx6q: Add support for Zealz GK802

Add support for the GK802 'QUAD CORE Mini PC', which seems to be loosely
based on the Freescale i.MX6Q HDMI dongle reference design.
It is supposedly identical to the Hiapad Hi802.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: Philipp Zabel <philipp.zabel@gmail.com>
Signed-off-by: Shawn Guo <shawn.guo@linaro.org>