ARM: dts: Add support for emtrion emCON-MX6 series

This patch adds support for the emtrion GmbH emCON-MX6 modules.
They are available with imx.6 Solo, Dual-Lite, Dual and Quad
equipped with Memory from 512MB to 2GB (configured by U-Boot).

Our default developer-Kit ships with the Avari baseboard and the
EDT ETM0700G0BDH6 Display (imx6[q|dl]-emcon-avari).

The devicetree is split into the common part providing all module
components and the basic support for all SoC versions
(imx6qdl-emcon.dtsi) and parts which are i.mx6 S|DL and D|Q relevant.
Finally the support for the avari baseboard in the developer-kit
configuration is provided by the emcon-avari dts files.

Signed-off-by: Jan Tuerk <jan.tuerk@emtrion.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>