ASoC: soc-core: accept zero format at snd_soc_runtime_set_dai_fmt()

Do nothing if format was zero at snd_soc_runtime_set_dai_fmt().
soc-core.c can be more simple code by this patch.

Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Link: https://lore.kernel.org/r/87ee8jt7d3.wl-kuninori.morimoto.gx@renesas.com


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