This is useful for userspace utilities which wish to use the previous
interface, specifically for micromanaging the increase/decrease steps by
setting min == max.
Reviewed-by: NChris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: NBen Widawsky <ben@bwidawsk.net>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>