There will be build failure because of EFI_AP_PROCEDURE definition
not found if MpInformation2.h is included by base type library.
MpInformation2.h depends on MpService.h because of
EFI_PROCESSOR_INFORMATION definition, and then MpService.h
depends on PiMultiPhase.h because of EFI_AP_PROCEDURE definition.
This patch updates MpInformation2.h to include PiMultiPhase.h instead
of PiPei.h and also removes SecPlatformInformation.h including.
It also does minor refinement to file header description.
Signed-off-by: Star Zeng <star.zeng@intel.com>