1. CapsuleLongModeBuffer variable should not have EFI_VARIABLE_RUNTIME_ACCESS attribute.

1.	CapsuleLongModeBuffer variable should not have EFI_VARIABLE_RUNTIME_ACCESS attribute.
2.	CapsuleLongModeBuffer variable should be set to Read-Only.  It should not be changed by someone else.
3.	Introduce a new PCD PcdIdentifyMappingPageTablePtr to share the same range of page table between AcpiS3 and Capsule.
4.	Capsule stack size is allocated from PcdCapsulePeiLongModeStackSize.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Elvin Li <elvin.li@intel.com>
Signed-off-by: Jiewen Yao <jiewen.yao@intel.com>
git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@15909 6f19259b-4bc3-4df7-8a09-765794883524