ARM: dts: imx6q-utilite-pro: add hpd gpio

The hpd pin of the second hdmi connector of the Utilite Pro is wired
up to a gpio pin of the SoC. Reflect this in the device tree.

Signed-off-by: Christopher Spinrath <christopher.spinrath@rwth-aachen.de>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>