drm/i915: ring w/a initialisation for gen 9

Add framework for gen 9 HW WAs

v1: Changed SOC specific WA function to gen 9 common function (Req: Damien Lespiau)
Signed-off-by: Nick Hoath <nicholas.hoath@intel.com>
Reviewed-by: Damien Lespiau <damien.lespiau@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/intel_ringbuffer.c

@@ -873,6 +873,11 @@ static int chv_init_workarounds(struct intel_engine_cs *ring)
 	return 0;
 }
 
+static int gen9_init_workarounds(struct intel_engine_cs *ring)
+{
+	return 0;
+}
+
 int init_workarounds_ring(struct intel_engine_cs *ring)
 {
 	struct drm_device *dev = ring->dev;
@@ -888,6 +893,9 @@ int init_workarounds_ring(struct intel_engine_cs *ring)
 	if (IS_CHERRYVIEW(dev))
 		return chv_init_workarounds(ring);
 
+	if (IS_GEN9(dev))
+		return gen9_init_workarounds(ring);
+
 	return 0;
 }