arm64: versal: zynqmp: Add support for VPXA2785

arm64: versal: zynqmp: Add support for VPXA2785

VPXA2785(vp-x-a2785-00) is evaluation board which contains two PCIe-Edge
fingers, one for PCIe-B(gen5x8) and one for CPM(dual gen5x8, gen5x16).
Each of the ports can operate in endpoint or root port mode. This allows
the single card to be used for both root port, endpoint, and switch modes.

The board is designed in the similar manner as others Versal boards. It
means board also have ZynqMP Zu4 System Controller which is described in a
separate file.

Signed-off-by: Michal Simek <michal.simek@xilinx.com>