boards: amd: Add generic APU board support for Versal Net SoC (Cortex-A78)

Introduce a generic board configuration for the APU on the Versal Net SoC,
which is based on the ARM Cortex-A78 processor.

This board setup provides a baseline environment for enabling and testing
Cortex-A78 features and peripheral integration on the APU subsystem.

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