arm64: dts: add support for NXP i.MX8MP FRDM board

arm64: dts: add support for NXP i.MX8MP FRDM board

The FRDM-i.MX8MP is an NXP development platform based on the i.MX8M Plus
SoC, featuring a quad Cortex-A53, Cortex-M7 co-processor, 4GB LPDDR4,
32GB eMMC, Wi-Fi 6/Bluetooth 5.4/802.15.4 tri-radio, Ethernet, HDMI/MIPI
display interfaces, camera connectors, and standard expansion headers.

Based on the device tree found in the NXP repository at github
https://github.com/nxp-imx-support/meta-imx-frdm and on imx8mp-evk
board kernel mainline device tree.

This is a basic device tree supporting:

 - Quad Cortex-A53
 - 4GB LPDDR4 DRAM
 - PCA9450C PMIC with regulators
 - Two NXP PCAL6416 GPIO expanders
 - RGB LEDs via GPIO expander
 - I2C1, I2C2, I2C3 controllers
 - UART2 (console) and UART3 (with RTS/CTS)
 - USDHC3 (8-bit eMMC)
 - SNVS power key (onboard power button)

Co-developed-by: Xiaofeng Wei <xiaofeng.wei@nxp.com>
Signed-off-by: Xiaofeng Wei <xiaofeng.wei@nxp.com>
Signed-off-by: Rogerio Pimentel <rpimentel.silva@gmail.com>
Acked-by: Krzysztof Kozlowski <krzk@kernel.org>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>