ASoC: qdsp6: q6afe-dai: Do not overwrite slim dai num_channels

num_channels for slim dais are aready set int set_channel_map,
do not overwrite them in hw_params.

Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Signed-off-by: Mark Brown <broonie@kernel.org>