x86, efi: Consolidate EFI nx control

The core EFI code and 64-bit EFI code currently have independent
implementations of code for setting memory regions as executable or not.
Let's consolidate them.

Signed-off-by: Matthew Garrett <mjg@redhat.com>
Link: http://lkml.kernel.org/r/1304623186-18261-2-git-send-email-mjg@redhat.com


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