usb: typec: tcpm: Release the role mux when exiting

The ref count for the USB role switch device must be
released after we are done using the switch.

Fixes: c6962c29 ("usb: typec: tcpm: Set USB role switch to device mode when configured as such")
Signed-off-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>