greybus: connection: remove WARN_ON from destroy

Remove WARN_ON from connection destroy testing for a NULL-connection
when destroying a connection.

This will allow for simpler driver code when releasing driver-managed
connections.
Reviewed-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Johan Hovold <johan@hovoldconsulting.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>

drivers/staging/greybus/connection.c

@@ -507,7 +507,7 @@ void gb_connection_destroy(struct gb_connection *connection)
 {
 	struct ida *id_map;
 
-	if (WARN_ON(!connection))
+	if (!connection)
 		return;
 
 	spin_lock_irq(&gb_connections_lock);