drm/i915: use staged outuput config in tv->mode_fixup

The "is this encoder cloned" check will be reused by the lvds encoder,
hence exract it.

v2: Be a bit more careful about that we need to check the new, staged
ouput configuration in the check_non_cloned helper ...

v3: Kill the double negation with s/!non_cloned/is_cloned/, suggested
by Jesse Barnes.

Reviewed-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
diff --git a/drivers/gpu/drm/i915/intel_tv.c b/drivers/gpu/drm/i915/intel_tv.c
index 98ad7fd..003ef9e 100644
--- a/drivers/gpu/drm/i915/intel_tv.c
+++ b/drivers/gpu/drm/i915/intel_tv.c
@@ -910,17 +910,14 @@
 		    const struct drm_display_mode *mode,
 		    struct drm_display_mode *adjusted_mode)
 {
-	struct drm_device *dev = encoder->dev;
 	struct intel_tv *intel_tv = enc_to_intel_tv(encoder);
 	const struct tv_mode *tv_mode = intel_tv_mode_find(intel_tv);
-	struct intel_encoder *other_encoder;
 
 	if (!tv_mode)
 		return false;
 
-	for_each_encoder_on_crtc(dev, encoder->crtc, other_encoder)
-		if (&other_encoder->base != encoder)
-			return false;
+	if (intel_encoder_check_is_cloned(&intel_tv->base))
+		return false;
 
 	adjusted_mode->clock = tv_mode->clock;
 	return true;