boards: amd: Add board support for the versalnet rpu on Versal net SOC

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

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