drm/i915: Fix comments about GMBUSFREQ register

The comment about GMBUSFREQ is confused. The spec actually explains
the 4MHz thing perfectly by noting that the 4MHz divider values is
actually just bits [9:2] not [9:0], hence the divide by 1000 correct.
Replace the confused note with a quote from the spec, and eliminate
the duplicated comment that snuck in.
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1461689194-6079-4-git-send-email-ville.syrjala@linux.intel.comReviewed-by: Mika Kahola <mika.kahola@intel.com>

drivers/gpu/drm/i915/intel_display.c

@@ -5329,18 +5329,13 @@ static void intel_update_cdclk(struct drm_device *dev)
 			 dev_priv->cdclk_freq);
 
 	/*
-	 * Program the gmbus_freq based on the cdclk frequency.
-	 * BSpec erroneously claims we should aim for 4MHz, but
-	 * in fact 1MHz is the correct frequency.
+	 * 9:0 CMBUS [sic] CDCLK frequency (cdfreq):
+	 * Programmng [sic] note: bit[9:2] should be programmed to the number
+	 * of cdclk that generates 4MHz reference clock freq which is used to
+	 * generate GMBus clock. This will vary with the cdclk freq.
 	 */
-	if (IS_VALLEYVIEW(dev) || IS_CHERRYVIEW(dev)) {
-		/*
-		 * Program the gmbus_freq based on the cdclk frequency.
-		 * BSpec erroneously claims we should aim for 4MHz, but
-		 * in fact 1MHz is the correct frequency.
-		 */
+	if (IS_VALLEYVIEW(dev_priv) || IS_CHERRYVIEW(dev_priv))
 		I915_WRITE(GMBUSFREQ_VLV, DIV_ROUND_UP(dev_priv->cdclk_freq, 1000));
-	}
 
 	if (dev_priv->max_cdclk_freq == 0)
 		intel_update_max_cdclk(dev);