PcAtChipsetPkg: AcpiTimerLib: Added StandaloneMm instance of AcpiTimerLib

This change added a new instance of AcpiTimerLib for StandaloneMm core
and drivers. It centralizes the common routines into shared files and
abstract the library constructor into corresponding files to accommodate
each constructor function prototypes.

Cc: Ray Ni <ray.ni@intel.com>

Signed-off-by: Kun Qin <kun.q@outlook.com>
Reviewed-by: Ray Ni <ray.ni@intel.com>

PcAtChipsetPkg/Library/AcpiTimerLib/DxeAcpiTimerLib.inf

@@ -25,6 +25,8 @@
 [Sources]
   AcpiTimerLib.c
   DxeAcpiTimerLib.c
+  DxeStandaloneMmAcpiTimerLib.c
+  DxeStandaloneMmAcpiTimerLib.h
 
 [Packages]
   MdePkg/MdePkg.dec