ArmPlatformPkg: fixups for 64-bit pointers

ArmPlatformPkg: fixups for 64-bit pointers

This retypes some stack base PCD as 64-bit, and fixes up a number of references
to 64-bit PCDs (including the retypes ones), to use the correct PcdGet64()
accessors. Note that, in the case of FixedPcdGet64, this does not actually
caused any problems, since that resolves to an immediate value. But the
generic PcdGetxx accessors should be typed according to the size of the PCD.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Leo Duran <leo.duran@amd.com>
[ard.biesheuvel: fixed up some instances in the 32-bit ARM code]
Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>