ASoC: soc-core.c: add index on snd_soc_of_get_dai_name()

Current snd_soc_of_get_dai_name() doesn't accept index
for #sound-dai-cells. It is not useful for user.
This patch adds it.

Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Link: https://lore.kernel.org/r/87pm5qdgng.wl-kuninori.morimoto.gx@renesas.com


Signed-off-by: Mark Brown <broonie@kernel.org>