MdeModulePkg: enforce arch-specific alignment for split regions

The splitting of memory regions into code and data regions violates
architecture specific alignment rules by using a fixed alignment
of 4 KB. Replace it with EFI_ACPI_RUNTIME_PAGE_ALLOCATION_ALIGNMENT,
which is defined appropriately on each architecture.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Reviewed-by: "Jaben Carsey" <jaben.carsey@intel.com>
Reviewed-by: "Yao, Jiewen" <Jiewen.Yao@intel.com>
git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@17812 6f19259b-4bc3-4df7-8a09-765794883524