ASoC: fsl: imx-audmix: Use devm_kcalloc() instead of devm_kzalloc()

A multiplication for the size determination of a memory allocation
indicated that an array data structure should be processed.
Thus use the corresponding function "devm_kcalloc".

Signed-off-by: Xu Wang <vulab@iscas.ac.cn>
Link: https://lore.kernel.org/r/20200921015918.24157-1-vulab@iscas.ac.cn


Signed-off-by: Mark Brown <broonie@kernel.org>