drm/i915/vlv: no MCHBAR on VLV

So don't try to allocate and program it, we're only fooling ourselves.
Reported-by: "Chang, Junxiao" <junxiao.chang@intel.com>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Reviewed-by: Junxiao Chang <junxiao.chang@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_dma.c

@@ -1187,6 +1187,9 @@ intel_setup_mchbar(struct drm_device *dev)
 	u32 temp;
 	bool enabled;
 
+	if (IS_VALLEYVIEW(dev))
+		return;
+
 	dev_priv->mchbar_need_disable = false;
 
 	if (IS_I915G(dev) || IS_I915GM(dev)) {