ArmPkg: Purge unused/unneeded CPU-specific header files

ArmPkg: Purge unused/unneeded CPU-specific header files

In ArmPkg/Include/Chipset, several CPU-specific header files reside.
Most of these provide no actual, or very little, use.
ARM1176JZ-S.h   is not used at all (and unusable since SVN r18237).
ArmAemV8.h      simply includes AArch64.h.
ArmCortexA15.h  defines one processor-specific configuration bit and
                then includes ArmV7.h.

Delete these include files, and update their sole users to function
without them.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Leif Lindholm <leif.lindholm@linaro.org>
Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@18736 6f19259b-4bc3-4df7-8a09-765794883524