Platform/AMD/XilinxBoard/ZynqMp/VirtualPkg: Add virtual ZynqMP board

Add an empty board based on Silicon/AMD/Xilinx/ZynqMpPkg.
This board contains empty devictree file, and has the
following features:

- Only 2GB DDR with no extra memory
- Uses SDHCI1 and UART1
- TF-A is located by the end of DDR
- Doesn't use OP-TEE

Relevant PCDs are set accordingly in VirtualPkg.dsc

This can be used as a reference for users to port EDK-II to
ZynqMP-based boards.

Signed-off-by: Mariam Elshakfy <mariam.elshakfy@linaro.org>