drm/i915: Add HAS_CORE_RING_FREQ macro

Added a new HAS_CORE_RING_FREQ macro, currently used in
gen6_update_ring_freq & i915_ring_freq_table debugfs function.
The programming & read of ring frequency table is needed for newer
GEN(>=6) platforms, except VLV/CHV.

Issue: VIZ-5144
Suggested-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Akash Goel <akash.goel@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/intel_pm.c

@@ -5104,7 +5104,7 @@ void gen6_update_ring_freq(struct drm_device *dev)
 {
 	struct drm_i915_private *dev_priv = dev->dev_private;
 
-	if (INTEL_INFO(dev)->gen < 6 || IS_VALLEYVIEW(dev))
+	if (!HAS_CORE_RING_FREQ(dev))
 		return;
 
 	mutex_lock(&dev_priv->rps.hw_lock);