efi: Add support for UEFIv2.5 Properties table

Version 2.5 of the UEFI spec introduces a new configuration table
called the 'EFI Properties table'. Currently, it is only used to
convey whether the Memory Protection feature is enabled, which splits
PE/COFF images into separate code and data memory regions.

Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Leif Lindholm <leif.lindholm@linaro.org>
Acked-by: Dave Young <dyoung@redhat.com>
Signed-off-by: Matt Fleming <matt.fleming@intel.com>