EFI_PEI_MP_SERVICES2_PPI has been added to MdePkg.
This PPI earlier existed as EDKII_PEI_MP_SERVICES2_PPI in UefiCpuPkg.
EDKII_PEI_MP_SERVICES2_PPI structure and PPI GUID are provided as
references for backwards compatibility.
Signed-off-by: Sachin Ganesh <sachinganesh@ami.com>