arm64: dts: imx: add imx8qm common dts file

The i.MX8QuadMax is a Dual (2x) Cortex-A72 and Quad (4x) Cortex-A53
proccessor with powerful graphic and multimedia features. It uses
the same architecture as MX8QXP, so many SS can be reused.
This patch adds i.MX8QuadMax SoC dtsi file.

Cc: Rob Herring <robh+dt@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: devicetree@vger.kernel.org
Cc: Sascha Hauer <kernel@pengutronix.de>
Cc: Fabio Estevam <fabio.estevam@nxp.com>
Signed-off-by: Dong Aisheng <aisheng.dong@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>