UefiCpuPkg/CpuDxe: Startup APs
    
    This sequence should happen:
    * CpuMp.c: Allocate a stack for the APs
    * ApStartup.c: Send Start IPI to wake APs in 16-bit real mode
    * MpAsm.S: AP enters CpuDxe driver code without stack
      - AP grabs a lock
      - AP sets up stack
      - AP calls CpuMp.c:ApEntryPointInC
    
    Contributed-under: TianoCore Contribution Agreement 1.0
    Signed-off-by: Jordan Justen <jordan.l.justen@intel.com>
    Signed-off-by: Chen Fan <chen.fan.fnst@cn.fujitsu.com>
    Reviewed-by: Jeff Fan <jeff.fan@intel.com>
    
    git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@16370 6f19259b-4bc3-4df7-8a09-765794883524