soc: amd: Add support for AMD Versal NET RPU

Add support for the RPU, real-time processing unit on Versal NET SoC.
It is based on Cortext-R52 processor.

The patch contains initial wiring and configuration for generic board
with OCM(1MB) and DDR(2G) memories, cpu, interrupt controller, global
timer and UART.

versalnet.dtsi contains common peripherals integrated into Versal NET
SoC, and versalnet_r52.dtsi has peripherals which are private to
Cortex-R52 processor.

Signed-off-by: Appana Durga Kedareswara rao <appana.durga.kedareswara.rao@amd.com>
Signed-off-by: Mubin Sayyed <mubin.sayyed@amd.com>