UefiCpuPkg/MpInitLib: Add microcode definitions defined in IA32 SDM

UefiCpuPkg/MpInitLib: Add microcode definitions defined in IA32 SDM

Add microcode definitions defined in Intel(R) 64 and IA-32 Architectures
Software Developer's Manual Volume 3A, Section 9.11.

v4:
  1. ProcessorSignature type changed to CPU_MICROCODE_PROCESSOR_SIGNATURE
  2. Add pack(1) for structure CPU_MICROCODE_HEADER and
     CPU_MICROCODE_EXTENDED_TABLE.
v3:
  1. Update SDM date to June, 2016
  2. Mention BCD format in CPU_MICROCODE_DATE
  3. Rename ProcessorChecksum to Checksum to match SDM.

Cc: Michael Kinney <michael.d.kinney@intel.com>
Cc: Feng Tian <feng.tian@intel.com>
Cc: Giri P Mudusuru <giri.p.mudusuru@intel.com>
Cc: Laszlo Ersek <lersek@redhat.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Jeff Fan <jeff.fan@intel.com>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Michael Kinney <michael.d.kinney@intel.com>
Reviewed-by: Giri P Mudusuru <giri.p.mudusuru@intel.com>
Tested-by: Laszlo Ersek <lersek@redhat.com>
Tested-by: Michael Kinney <michael.d.kinney@intel.com>