arch: arm64: dts: Add support for AM69 Starter Kit

AM69 Starter Kit is a single board designed for TI AM69 SOC that
provides advanced system integration in automotive ADAS applications,
autonomous mobile robot and edge AI applications. The SOC comprises
of Cortex-A72s in dual clusters, lockstep capable dual Cortex-R5F MCUs,
Vision Processing Accelerators (VPAC) with Image Signal Processor (ISP)
and multiple vision assist accelerators, Depth and Motion Processing
Accelerators (DMPAC), Deep-learning Matrix Multiply Accelerator(MMA)
and C7x floating point vector DSP

AM69 SK supports the following interfaces:
       * 32 GB LPDDR4 RAM
       * x1 Gigabit Ethernet interface
       * x3 USB 3.0 Type-A ports
       * x1 USB 3.0 Type-C port
       * x1 UHS-1 capable micro-SD card slot
       * x4 MCAN instances
       * 32 GB eMMC Flash
       * 512 Mbit OSPI flash
       * x2 Display connectors
       * x1 PCIe M.2 M Key
       * x1 PCIe M.2 E Key
       * x1 4L PCIe Card Slot
       * x3 CSI2 Camera interface
       * 40-pin Raspberry Pi header

Add initial support for the AM69 SK board.

Design Files: https://www.ti.com/lit/zip/SPRR466
TRM: https://www.ti.com/lit/zip/spruj52



Signed-off-by: Dasnavis Sabiya <sabiya.d@ti.com>
Signed-off-by: Vignesh Raghavendra <vigneshr@ti.com>
Link: https://lore.kernel.org/r/20230119132958.124435-3-sabiya.d@ti.com