drm/msm: only register 'kms' debug file if KMS is used

There is little point in having the empty debugfs file which always
returns -ENODEV. Change this file to be created only if KMS is actually
used.
Reviewed-by: Rob Clark <robdclark@gmail.com>
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Patchwork: https://patchwork.freedesktop.org/patch/561656/Signed-off-by: Rob Clark <robdclark@chromium.org>

drivers/gpu/drm/msm/msm_debugfs.c

@@ -314,8 +314,9 @@ void msm_debugfs_init(struct drm_minor *minor)
 	debugfs_create_file("gpu", S_IRUSR, minor->debugfs_root,
 		dev, &msm_gpu_fops);
 
-	debugfs_create_file("kms", S_IRUSR, minor->debugfs_root,
-		dev, &msm_kms_fops);
+	if (priv->kms)
+		debugfs_create_file("kms", S_IRUSR, minor->debugfs_root,
+				    dev, &msm_kms_fops);
 
 	debugfs_create_u32("hangcheck_period_ms", 0600, minor->debugfs_root,
 		&priv->hangcheck_period);