xlat: added xlat table mock structures and helpers

XLAT table mock structures and helpers are added since they are
to be used by further tests.

Signed-off-by: Juan Pablo Conde <juanpablo.conde@arm.com>
Co-developed-by: Kathleen Capella <kathleen.capella@arm.com>
Change-Id: I5e60f5d54e2376e914c8e264944aa624d848d02c
10 files changed