ArmVirtPkg/ArmVirtQemu: use first 128 MiB as permanent PEI memory

ArmVirtPkg/ArmVirtQemu: use first 128 MiB as permanent PEI memory

In order to allow booting with the MMU and caches enabled really early,
we need to ensure that the code that populates the page tables can
access those page tables with the statically defined ID map active.

So let's put the permanent PEI RAM in the first 128 MiB of memory, which
we will cover with this initial ID map (as it is the minimum supported
DRAM size for ArmVirtQemu).

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>