ArmPkg/ArmV7Mmu: prefer non shareable memory on non-coherent hardware

ArmPkg/ArmV7Mmu: prefer non shareable memory on non-coherent hardware

Commit SVN r18778 made all mappings of normal memory (inner) shareable,
even on hardware that implements shareability as uncached accesses.
The original concerns that prompted the change, regarding coherent DMA
and virt guests migrating between CPUs, do not apply to such hardware,
so revert to the original behavior in that case.

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@19285 6f19259b-4bc3-4df7-8a09-765794883524