ARM: dts: imx6qdl: Add HDMI to TQMa6x/MBa6

This adds support for a COTS monitor connected to X17.
4k monitors can be used, but are limited to 1080p.

Signed-off-by: Alexander Stein <alexander.stein@ew.tq-group.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>