ARM: dts: imx6qdl: move HDMI controller to right location in DT

Currently the HDMI controller is a child device of the AIPS bus in the
DT which is clearly wrong. Move it to the right location.
This introduces no functional change it just aligns the DT representation
with reality.

Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
Signed-off-by: Shawn Guo <shawn.guo@linaro.org>