drm/i915: Change CHV SKU400 GPU freq divider to 10

According to "Cherryview_GFXclocks_y14w36d1.xlsx" the GPU frequency
divider should be 10 in when the CZ clock is 400 MHz. Change the code
to agree so that we report the correct frequencies.
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Deepak S<deepak.s@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/intel_pm.c

@@ -7215,8 +7215,9 @@ static int vlv_gpu_freq_div(unsigned int czclk_freq)
 		return 12;
 	case 320:
 	case 333:
-	case 400:
 		return 16;
+	case 400:
+		return 20;
 	default:
 		return -1;
 	}