Various urgent EFI fixes and some warning cleanups for v3.8

  * EFI boot stub fix for Macbook Pro's from Maarten Lankhorst
  * Fix an oops in efivarfs from Lingzhu Xiang
  * 32-bit warning cleanups from Jan Beulich
  * Patch to Boot on >512GB RAM systems from Nathan Zimmer
  * Set efi.runtime_version correctly
  * efivarfs updates

Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>