MdeModulePkg: use correct granularity when allocating pool pages

MdeModulePkg: use correct granularity when allocating pool pages

After fixing the sanity check on the alignment of the runtime regions
in SVN revision #16630 ("MdeModulePkg/DxeMain: Fix wrong sanity check
in CoreTerminateMemoryMap()"), it is no longer possible to define a
runtime allocation alignment that is different from the boot time
allocation alignment.

For instance, #defining the following in MdeModulePkg/Core/Dxe/Mem/Imem.h
will hit the ASSERT () in MdeModulePkg/Core/Dxe/Mem/Page.c:1798

  #define EFI_ACPI_RUNTIME_PAGE_ALLOCATION_ALIGNMENT  (SIZE_64KB)
  #define DEFAULT_PAGE_ALLOCATION                     (EFI_PAGE_SIZE)

(which is needed for 64-bit ARM to adhere to the Server Base Boot
Requirements [SBBR], which stipulates that all runtime memory regions
should be naturally aligned multiples of 64 KB)

This patch fixes this use case by ensuring that the backing for the memory
pools is allocated in appropriate chunks for the memory type.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Reviewed-by: Liming Gao <liming.gao@intel.com>
git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@17011 6f19259b-4bc3-4df7-8a09-765794883524