These functions are used for the PSCI implementation and are needed to
build BL31, but we cannot implement them until we add several more drivers
related to ti-sci so these are only stubs for now.

Signed-off-by: Nishanth Menon <nm@ti.com>
Signed-off-by: Benjamin Fair <b-fair@ti.com>
Signed-off-by: Andrew F. Davis <afd@ti.com>