ASoC: rsnd: don't overwrite io on rsnd_cmd_init()

Current rsnd_cmd_init() overwrites "io" which will be used end of this
function. This patch solved this issue.

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