UefiCpuPkg/CpuMpPei: Remove PmodeOffset and LmodeOffset

UefiCpuPkg/CpuMpPei: Remove PmodeOffset and LmodeOffset

Remove Pmode(Entry)Offset/Lmode(Entry)Offset and use unified Mode(Entry)Offset
to clean up the definition of MP_ASSEMBLY_ADDRESS_MAP and MP_CPU_EXCHANGE_INFO.

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