UefiCpuPkg/SilvermontMsr.h: add MSR reference from SDM in comment
UefiCpuPkg/SilvermontMsr.h: add MSR reference from SDM in comment

Cc: Michael Kinney <fd20bc543a9f65bb633fac7d08a403c1f1c8eb6c@intel.com>
Cc: Feng Tian <e66bb7e9f36c82a029035c5885acf75500d07e68@intel.com>
Cc: Giri P Mudusuru <25c53ebec15b492d82d7bf064153464c6e8fbfec@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Jeff Fan <7d6fed0251a47076d6e691789131f22f07d057b4@intel.com>
Reviewed-by: Giri P Mudusuru <25c53ebec15b492d82d7bf064153464c6e8fbfec@intel.com>

MattDevo/edk2,MattDevo/edk2,MattDevo/edk2,MattDevo/edk2,MattDevo/edk2,MattDevo/edk2,MattDevo/edk2,MattDevo/edk2