board: phytec: am62x: Add PHYTEC phyCORE-AM62x SoM

Add basic support for PHYTEC phyCORE-AM62x SoM.

Supported features:
  - 2GB DDR4 RAM
  - eMMC Flash
  - OSPI NOR Flash
  - external uSD
  - Ethernet
  - debug UART

Product page SoM: https://www.phytec.com/product/phycore-am62x



Device trees were taken from Linux v6.7-rc3.

Signed-off-by: Wadim Egorov <w.egorov@phytec.de>
Reviewed-by: Dhruva Gole <d-gole@ti.com>