Add device trees for the MBa6x mainboard with TQMa6Q/QP/DL SoMs.

As discussed, all new files are added with GPL-2.0-only license, as they
are too tightly intertwined with the SoC DTSIs imx6dl.dtsi and imx6q.dtsi,
which are GPL-2.0.
Signed-off-by: Markus Niebel <Markus.Niebel@ew.tq-group.com>
Signed-off-by: Matthias Schiffer <matthias.schiffer@ew.tq-group.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>