The stacks must be 32-bit aligned (which is not the case of 0xFFFFFFFF). This change ensures the stacks are setup properperly in case the system memory is available at 0xFFFFFFFF. git-svn-id: https://edk2.svn.sourceforge.net/svnroot/edk2/trunk/edk2@13057 6f19259b-4bc3-4df7-8a09-765794883524