ArmVirtPkg/MemoryInitPeiLib: split memory HOB based on MAX_ALLOC_ADDRESS

ArmVirtPkg/MemoryInitPeiLib: split memory HOB based on MAX_ALLOC_ADDRESS

The current ArmVirtMemoryInitPeiLib code splits the memory region passed
via PcdSystemMemoryBase/PcdSystemMemorySize in two if the region extends
beyond the MAX_ADDRESS limit. This was introduced for 32-bit ARM, which
may support more than 4 GB of physical address space, but cannot address
all of it via a 1:1 mapping, and a single region that is not mappable
in its entirety is unusable by the PEI core.

AArch64 is in a similar situation now: platforms may support more than
256 TB of physical address space, but only 256 TB is addressable by the
CPU, and so a memory region that extends from below this limit to above
it should be split.

Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>