MdeModulePkg: use 64 KB granularity for runtime allocations on AArch64

MdeModulePkg: use 64 KB granularity for runtime allocations on AArch64

On AArch64, the OS can choose to run with a page size of 64 KB,
making it cumbersome to deal with UEFI reserved memory regions
whose boundaries are not 64 KB aligned.

So increase the allocation granularity for runtime regions to
64 KB.

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@17016 6f19259b-4bc3-4df7-8a09-765794883524