ASoC: rsnd: care return value from rsnd_node_fixed_index()

ASoC: rsnd: care return value from rsnd_node_fixed_index()

Renesas Sound is very complex, and thus it needs to use
rsnd_node_fixed_index() to know enabled pin index.

It returns error if strange pin was selected,
but some codes didn't check it.

This patch 1) indicates error message, 2) check return
value.

Reported-by: kernel test robot <lkp@intel.com>
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Link: https://lore.kernel.org/r/87pmlbgn5t.wl-kuninori.morimoto.gx@renesas.com
Signed-off-by: Mark Brown <broonie@kernel.org>