Let's be more conservative and protect platforms that don't
support PSR from unecessary interactions.
Reviewed-by: NVijay Purushothaman <vijay.a.purushothaman@intel.com>
Signed-off-by: NRodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>