drm/i915: Use pipe_name() instead of the pipe number

Yet other direct usages of the pipe number instead of pipe_name().
We've been tracking them lately but managed to miss these last ones.

v2: Catch them all! (Ville)

Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com> (v1)
Signed-off-by: Damien Lespiau <damien.lespiau@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
diff --git a/drivers/gpu/drm/i915/intel_panel.c b/drivers/gpu/drm/i915/intel_panel.c
index 1f29960..de15186 100644
--- a/drivers/gpu/drm/i915/intel_panel.c
+++ b/drivers/gpu/drm/i915/intel_panel.c
@@ -574,7 +574,7 @@
 		intel_pipe_to_cpu_transcoder(dev_priv, pipe);
 	unsigned long flags;
 
-	DRM_DEBUG_KMS("pipe=%d\n", pipe);
+	DRM_DEBUG_KMS("pipe %c\n", pipe_name(pipe));
 
 	spin_lock_irqsave(&dev_priv->backlight.lock, flags);