ASoC: simple-card: un-implemented set_fmt is not error

Current simple-card returns error if DAI doesn't
support .set_fmt callback.
But the error is -ENOTSUPP (= not supported),
and it is not error.
This patch avoids such case

Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Signed-off-by: Mark Brown <broonie@linaro.org>