ArmPlatformPkg: remove ArmGlobalVariable PCD, GUID and PPI definitions

ArmPlatformPkg: remove ArmGlobalVariable PCD, GUID and PPI definitions

Now that we removed all references to the ArmGlobalVariable definitions
in the various lowlevel PrePi and PrePeiCore init routines, and removed
the PPI and HOB references from PlatformPeim, it is time to say goodbye
to ArmGlobalVariable. So remove the includes and the .DEC declarations.

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@19003 6f19259b-4bc3-4df7-8a09-765794883524