drm/i915: enable RC6 by default on Haswell

It should be working so let's turn it on by default and catch any possible
issues faster.
Signed-off-by: NEugeni Dodonov <eugeni.dodonov@intel.com>
Reviewed-by: NBen Widawsky <ben@bwidawsk.net>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/intel_pm.c

@@ -2334,9 +2334,11 @@ int intel_enable_rc6(const struct drm_device *dev)
 	if (INTEL_INFO(dev)->gen == 5)
 		return 0;
 
-	/* Sorry Haswell, no RC6 for you for now. */
+	/* On Haswell, only RC6 is available. So let's enable it by default to
+	 * provide better testing and coverage since the beginning.
+	 */
 	if (IS_HASWELL(dev))
-		return 0;
+		return INTEL_RC6_ENABLE;
 
 	/*
 	 * Disable rc6 on Sandybridge