Use rsp instead of esp to save 64-bit stack pointer.

Signed-off-by: Elvin Li <elvin.li@intel.com>
Reviewed-by: Liming Gao <liming.gao@intel.com>


git-svn-id: svn://svn.code.sf.net/p/edk2/code/trunk/edk2/MdePkg@14812 6f19259b-4bc3-4df7-8a09-765794883524