greybus: connection: silence warning on unbound protocols

If a protocol was not successfully created, we can't drop the refcount
on it. This might happen for example if the connection fails to bind a
protocol.

Silences a warning on cleanup.
Signed-off-by: Perry Hung <perry@leaflabs.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>

drivers/staging/greybus/connection.c

@@ -319,7 +319,8 @@ void gb_connection_destroy(struct gb_connection *connection)
 	list_del(&connection->hd_links);
 	spin_unlock_irq(&gb_connections_lock);
 
-	gb_protocol_put(connection->protocol);
+	if (connection->protocol)
+		gb_protocol_put(connection->protocol);
 	connection->protocol = NULL;
 
 	id_map = &connection->hd->cport_id_map;

drivers/staging/greybus/protocol.c

@@ -196,9 +196,6 @@ void gb_protocol_put(struct gb_protocol *protocol)
 	u8 minor;
 	u8 protocol_count;
 
-	if (WARN_ON(!protocol))
-		return;
-
 	id = protocol->id;
 	major = protocol->major;
 	minor = protocol->minor;