UefiCpuPkg/CpuMpPei: Fix pack(1) issue on x64 arch

UefiCpuPkg/CpuMpPei: Fix pack(1) issue on x64 arch

Packing alignment for MP_CPU_EXCHANGE_INFO should be 1. This should be typo when
check-in CpuMpPei driver. IA32 arch MP_CPU_EXCHANGE_INFO is luckly pack(1). It
leads CpuMpPei x64 version hung.

Contributed-under: TianoCore Contribution Agreement 1.0
Reported-by: Michael Kinney <michael.d.kinney@intel.com>
Cc: Feng Tian <feng.tian@intel.com>
Cc: Michael Kinney <michael.d.kinney@intel.com>
Cc: Jordan Justen <jordan.l.justen@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Jeff Fan <jeff.fan@intel.com>
Tested-by: Michael Kinney <michael.d.kinney@intel.com>
Reviewed-by: Michael Kinney <michael.d.kinney@intel.com>
git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@19340 6f19259b-4bc3-4df7-8a09-765794883524