ArmPkg/ArmMmuLib: take MAX_ALLOC_ADDRESS into account

ArmPkg/ArmMmuLib: take MAX_ALLOC_ADDRESS into account

When creating the page tables for the 1:1 mapping, ensure that we don't
attempt to map more than what is architecturally permitted when running
with 4 KB pages, which is 48 bits of VA. This will be reflected in the
value of MAX_ALLOC_ADDRESS once we override it for AArch64, so use that
macro instead of MAX_ADDRESS.

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