MdeModulePkg PiSmmCore: Only install EndOfS3Resume during S3 resume

MdeModulePkg PiSmmCore: Only install EndOfS3Resume during S3 resume

Otherwise, it may be triggered wrongly by other code in OS.

This patch is to use S3 entry callback to determine if it will be
during S3 resume, and check it in SmmReadyToBootHandler().

Cc: Jiewen Yao <jiewen.yao@intel.com>
Cc: Eric Dong <eric.dong@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Star Zeng <star.zeng@intel.com>
Reviewed-by: Jiewen Yao <jiewen.yao@intel.com>