drm/i915: disable rc6 on haswell for now

This needs proper enablement to avoid machine hangs, so let's just avoid
it for now.
Reviewed-by: NRodrigo Vivi <rodrigo.vivi@gmail.com>
Signed-off-by: NEugeni Dodonov <eugeni.dodonov@intel.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/intel_display.c

@@ -8585,6 +8585,10 @@ 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. */
+	if (IS_HASWELL(dev))
+		return 0;
+
 	/*
 	 * Disable rc6 on Sandybridge
 	 */