ASoC: rsnd: gen: rsnd_gen_ops cares .probe and .remove

Current rsnd_gen_ops didn't care about .probe and .remove
functions, but it was not good sense.
This patch tidyup it

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