USB: typec: tcpm: create debugfs subdir for the driver

The single debugfs file for this driver really is a log file, so make a
subdir and call it "log" to make it obvious this is what it is for.
This makes cleanup simpler as we just remove the whole directory, no
need to handle individual files anymore.

Cc: Guenter Roeck <linux@roeck-us.net>
Cc: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Cc: linux-usb@vger.kernel.org
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Reviewed-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Link: https://lore.kernel.org/r/20210216144645.3813043-6-gregkh@linuxfoundation.orgSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/typec/tcpm/tcpm.c

@@ -709,8 +709,9 @@ static void tcpm_debugfs_init(struct tcpm_port *port)
 
 	mutex_init(&port->logbuffer_lock);
 	snprintf(name, NAME_MAX, "tcpm-%s", dev_name(port->dev));
-	port->dentry = debugfs_create_file(name, S_IFREG | 0444, usb_debug_root,
-					   port, &tcpm_debug_fops);
+	port->dentry = debugfs_create_dir(name, usb_debug_root);
+	debugfs_create_file("log", S_IFREG | 0444, port->dentry, port,
+			    &tcpm_debug_fops);
 }
 
 static void tcpm_debugfs_exit(struct tcpm_port *port)