ArmPkg/ArmLib: mark all cached mappings as (inner) shareable

ArmPkg/ArmLib: mark all cached mappings as (inner) shareable

Mark all cached memory mappings as shareable (or inner shareable on
AArch64) so that our view of memory is kept coherent by the hardware.

This is relevant for things like coherent DMA and virtualization (where
a guest may migrate to another core) but in general, since UEFI on ARM
is mostly used in a context where the secure firmware and possibly a
secure OS are already up and running, it is best to refrain from using
any non-shareable mappings.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Reviewed-by: Leif Lindholm <leif.lindholm@linaro.org>
git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@18778 6f19259b-4bc3-4df7-8a09-765794883524