It is observed on BSW that requesting a new frequency from Punit
does nothing when the GPU is in rc6, and if we let GPU enter rc6
with a high frequency, Vnn remains slightly higher than at minimum
frequency. Extending vlv_set_rps_idle() workaround on CHV/BSW.

v2: Update commit msg (Ville)
suggested-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Deepak S <deepak.s@linux.intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>