plat: add platform-specific mocks

Platform-specific mocks are added so they can be used in further
tests.

Signed-off-by: Juan Pablo Conde <juanpablo.conde@arm.com>
Co-developed-by: Kathleen Capella <kathleen.capella@arm.com>
Change-Id: I4cdfcb0a63705f61569ad58668a25db611b5f9e1
1 file changed