Setting a floor can ensure a minimum experience
level. The 450MHz value came from a power and
performance study of various types of workloads
(3D, Media, GPGPU, idle, etc).
v2: rebased
Signed-off-by: Tom O'Rourke <Tom.O'Rourke@intel.com> Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk> Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>