ASoC: rsnd: select each SRC correctly for CMD data path

To select CMD data patch, it should use correct SRC from each stream
in MUX case. But current code is selecting SRC from fixed stream.
This patch solves this issue.

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