usb: typec: Prepare alt mode enter/exit reporting for UCSI alt mode support

Because of UCSI, we have to support alt mode enter/exit
reporting even when there is no alt mode driver bind to the
alt mode device. With UCSI a firmware handles the alternate
modes, and the modes are entered automatically from OS PoW.

Changing typec_altmode_update_active() so that the driver
module ref count is incremented/decremented only if there
really is a driver for the alt mode. That avoids a NULL
pointer dereference from happening when the driver is
missing.
Signed-off-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/typec/class.c

@@ -277,7 +277,7 @@ void typec_altmode_update_active(struct typec_altmode *adev, bool active)
 	if (adev->active == active)
 		return;
 
-	if (!is_typec_port(adev->dev.parent)) {
+	if (!is_typec_port(adev->dev.parent) && adev->dev.driver) {
 		if (!active)
 			module_put(adev->dev.driver->owner);
 		else