drm/i915: use render gen to switch ring irq functions

Top-level interrupt bits are usually found in the display block. It
therefore makes sense to use HAS_PCH_SPLIT in i915_irq.c

But the irq stuff in intel_ring.c only concerns itself with render
core/gt-level interrupt sources. It therefore makes more sense to
switch based on gpu gen.

Kills a vlv special case.
Reviewed-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-Off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/intel_ringbuffer.c

@@ -687,7 +687,7 @@ render_ring_get_irq(struct intel_ring_buffer *ring)
 
 	spin_lock(&ring->irq_lock);
 	if (ring->irq_refcount++ == 0) {
-		if (HAS_PCH_SPLIT(dev) || IS_VALLEYVIEW(dev))
+		if (INTEL_INFO(dev)->gen >= 5)
 			ironlake_enable_irq(dev_priv,
 					    GT_PIPE_NOTIFY | GT_USER_INTERRUPT);
 		else
@@ -706,7 +706,7 @@ render_ring_put_irq(struct intel_ring_buffer *ring)
 
 	spin_lock(&ring->irq_lock);
 	if (--ring->irq_refcount == 0) {
-		if (HAS_PCH_SPLIT(dev) || IS_VALLEYVIEW(dev))
+		if (INTEL_INFO(dev)->gen >= 5)
 			ironlake_disable_irq(dev_priv,
 					     GT_USER_INTERRUPT |
 					     GT_PIPE_NOTIFY);