drm/i915: don't set transcoder bpc on CougarPoint

This prevents us from setting reserved or incorrect bits on CougarPoint.
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Keith Packard <keithp@keithp.com>

drivers/gpu/drm/i915/intel_display.c

@@ -1158,12 +1158,15 @@ static void intel_enable_transcoder(struct drm_i915_private *dev_priv,
 
 	reg = TRANSCONF(pipe);
 	val = I915_READ(reg);
+
+	if (HAS_PCH_IBX(dev_priv->dev)) {
 		/*
 		 * make the BPC in transcoder be consistent with
 		 * that in pipeconf reg.
 		 */
 		val &= ~PIPE_BPC_MASK;
 		val |= I915_READ(PIPECONF(pipe)) & PIPE_BPC_MASK;
+	}
 	I915_WRITE(reg, val | TRANS_ENABLE);
 	if (wait_for(I915_READ(reg) & TRANS_STATE_ENABLE, 100))
 		DRM_ERROR("failed to enable transcoder %d\n", pipe);