ArmPlatformPkg: Introduce Primary core macros

ArmPlatformPkg: Introduce Primary core macros

On MpCore system, the primary core can now be any core of the system.

To identify the primary core, you can use 'gArmTokenSpaceGuid.PcdArmPrimaryCoreMask'
and 'gArmTokenSpaceGuid.PcdArmPrimaryCore'.
These PCDs by default use the ClusterId and CoreId to identify the core. And the
primary core is defined as the ClusetrId=0 and CoreId=0.

The helper macros are: IS_PRIMARY_CORE(MpId), GET_CORE_ID(MpId), GET_CLUSTER_ID(MpId),
GET_CORE_POS(MpId), PRIMARY_CORE_ID.

git-svn-id: https://edk2.svn.sourceforge.net/svnroot/edk2/trunk/edk2@12412 6f19259b-4bc3-4df7-8a09-765794883524