greybus: legacy: use protocol pointer to determine state

Use the protocol pointer to determine the legacy connection state.

This is needed to allow core disable connections when an interface has
been hot-unplugged without the legacy protocols leaking its resources.
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/legacy.c

@@ -100,7 +100,7 @@ static int legacy_connection_init(struct gb_connection *connection)
 
 static void legacy_connection_exit(struct gb_connection *connection)
 {
-	if (connection->state == GB_CONNECTION_STATE_DISABLED)
+	if (!connection->protocol)
 		return;
 
 	gb_connection_disable(connection);