drm/i915: DE_PCU_EVENT irq is ilk-only

Like all the other drps/ips stuff. Hence add the corresponding check,
give the function a preciser prefix and move the single reg clearing into
the rps handling function, too.
Reviewed-by: NBen Widawsky <ben@bwidawsk.net>
Reviewed-by: NDamien Lespiau <damien.lespiau@intel.com>
Reviewed-by: NChris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_irq.c

@@ -296,12 +296,14 @@ static void i915_hotplug_work_func(struct work_struct *work)
 	drm_helper_hpd_irq_event(dev);
 }
 
-static void i915_handle_rps_change(struct drm_device *dev)
+static void ironlake_handle_rps_change(struct drm_device *dev)
 {
 	drm_i915_private_t *dev_priv = dev->dev_private;
 	u32 busy_up, busy_down, max_avg, min_avg;
 	u8 new_delay = dev_priv->cur_delay;
 
+	I915_WRITE16(MEMINTRSTS, I915_READ(MEMINTRSTS));
+
 	I915_WRITE16(MEMINTRSTS, MEMINT_EVAL_CHG);
 	busy_up = I915_READ(RCPREVBSYTUPAVG);
 	busy_down = I915_READ(RCPREVBSYTDNAVG);
@@ -794,10 +796,8 @@ static irqreturn_t ironlake_irq_handler(DRM_IRQ_ARGS)
 			ibx_irq_handler(dev, pch_iir);
 	}
 
-	if (de_iir & DE_PCU_EVENT) {
-		I915_WRITE16(MEMINTRSTS, I915_READ(MEMINTRSTS));
-		i915_handle_rps_change(dev);
-	}
+	if (IS_GEN5(dev) &&  de_iir & DE_PCU_EVENT)
+		ironlake_handle_rps_change(dev);
 
 	if (IS_GEN6(dev) && pm_iir & GEN6_PM_DEFERRED_EVENTS)
 		gen6_queue_rps_work(dev_priv, pm_iir);