rcar: mux: Avoid use of ret uninitialised

We use ret as the return value from the rsnd_mix_probe() but if there
are no child nodes and no errors then we will never initialize ret leading
to build warnings. Ensure ret is initialized before we iterate over the
child nodes to avoid this.
Signed-off-by: Mark Brown <broonie@kernel.org>

sound/soc/sh/rcar/mix.c

@@ -158,6 +158,7 @@ int rsnd_mix_probe(struct rsnd_priv *priv)
 	priv->mix	= mix;
 
 	i = 0;
+	ret = 0;
 	for_each_child_of_node(node, np) {
 		mix = rsnd_mix_get(priv, i);