arm64: dts: freescale: Add i.MX8MP dtsi support

The i.MX8M Plus Media Applications Processor is part of the growing
mScale family targeting the consumer and industrial market. It brings
an effective Machine Learning and AI accelerator that enables a new
class of applications. It is built in Samsung 14LPP to achieve both
high performance and low power consumption and relies on a powerful
fully coherent core complex based on a quad core ARM Cortex-A53 cluster
and Cortex-M7 low-power coprocessor, audio digital signal processor,
machine learning and graphics accelerators.

Add the basic dtsi support for i.MX8MP.
Signed-off-by: Anson Huang <Anson.Huang@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>