drm/i915/skl: gen9 uses the same bind_vma() vfuncs as gen6+

Temporary plug a BUG() while waiting for a better solution. See:

  http://lists.freedesktop.org/archives/intel-gfx/2014-January/038132.html

However Chris was looking at cleaning-up this as well, so went for the
easy intermediate solution instead.
Reviewed-by: Ben Widawsky <ben@bwidawsk.net>
Signed-off-by: Damien Lespiau <damien.lespiau@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_gem_gtt.c

@@ -2130,6 +2130,7 @@ static struct i915_vma *__i915_gem_vma_create(struct drm_i915_gem_object *obj,
 	vma->obj = obj;
 
 	switch (INTEL_INFO(vm->dev)->gen) {
+	case 9:
 	case 8:
 	case 7:
 	case 6: