drm/i915: don't check plane vs pipe enable on ILK+

These bits have a different meaning on ILK+, where planes are hardwired
to pipes.  Fixing this avoid some spurious assertion failures.
Signed-off-by: NJesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>

drivers/gpu/drm/i915/intel_display.c

@@ -1225,6 +1225,10 @@ static void assert_planes_disabled(struct drm_i915_private *dev_priv,
 	u32 val;
 	int cur_pipe;
 
+	/* Planes are fixed to pipes on ILK+ */
+	if (HAS_PCH_SPLIT(dev_priv->dev))
+		return;
+
 	/* Need to check both planes against the pipe */
 	for (i = 0; i < 2; i++) {
 		reg = DSPCNTR(i);