drm/i915: Use czclk_freq in vlv c0 residency calculations
Replace the use of mem_freq/4 with czclk_freq in the vlv c0 residency
calculations.
Also deal with VLV_COUNT_RANGE_HIGH which affects all RCx residency
counters. We have just enough bits to do this without intermediate
divisions.
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com> Reviewed-by: Imre Deak <imre.deak@intel.com> Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>