disp: msm: dsi: check for null pointer during debugfs deinit

Add null pointer check for debugfs deinit during
unbind path. Additionally, fix debugfs init to
not free debugfs directory unintentionally.

Change-Id: I430fe8810608a8e56d6d02e996044e69b4116421
Signed-off-by: Shashank Babu Chinta Venkata <sbchin@codeaurora.org>

msm/dsi/dsi_display.c

@@ -2097,7 +2097,10 @@ error:
 
 static int dsi_display_debugfs_deinit(struct dsi_display *display)
 {
-	debugfs_remove_recursive(display->root);
+	if (display->root) {
+		debugfs_remove_recursive(display->root);
+		display->root = NULL;
+	}
 
 	return 0;
 }