ARM: add support for non-global kernel mappings

Add support to the kernel translation table population routines for
creating non-global mappings. This will be used by the UEFI runtime
services, which will use temporary mappings in the userland range.

Reviewed-by: Matt Fleming <matt@codeblueprint.co.uk>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>