VMM/ARM: Move the VBox ARMv8 platform descriptor from the end of the address space right after the UEFI region, bugref:10746
The original solution was to avoid as many hardcoded addresses as possible by placing the VBox region descriptor right at the end
of the guest physical address space. This turned out to be a bad idea because on M3 the host maximum physical address width and
guest maxmium physical address width differ so mapping the platform descriptor fails. Also saved states would not be portable if
a saved state is mvoed between systems with different physical address widths.
The solution is to move the platform descriptor right after the UEFI region and move the MMIO region, which grew from top to bottom
to start right after the base RAM region and grow upwards.
