ASoC: rsnd: Fix an error handling path in 'rsnd_node_count()'

If we return before the end of the 'for_each_child_of_node()' iterator, the
reference taken on 'np' must be released.

Add the missing 'of_node_put()' call.

Fixes: c413983e

 ("ASoC: rsnd: adjust disabled module")
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Reviewed-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Link: https://lore.kernel.org/r/4c0e893cbfa21dc76c1ede0b6f4f8cff42209299.1634586167.git.christophe.jaillet@wanadoo.fr
Signed-off-by: Mark Brown <broonie@kernel.org>