drm/i915: Disable the surface tile swizzling on Sandybridge.

I can't explain this, except that it makes my display correct.
Signed-off-by: Eric Anholt <eric@anholt.net>

drivers/gpu/drm/i915/intel_display.c

@@ -3419,7 +3419,7 @@ static int intel_crtc_mode_set(struct drm_crtc *crtc,
 
 	intel_wait_for_vblank(dev);
 
-	if (HAS_PCH_SPLIT(dev)) {
+	if (IS_IRONLAKE(dev)) {
 		/* enable address swizzle for tiling buffer */
 		temp = I915_READ(DISP_ARB_CTL);
 		I915_WRITE(DISP_ARB_CTL, temp | DISP_TILE_SURFACE_SWIZZLING);