ASoC: Intel: sst_byt: remove kfree for memory allocated with devm_kzalloc

It's not necessary to free memory allocated with devm_kzalloc
and using kfree leads to a double free.

Signed-off-by: Wei Yongjun <yongjun_wei@trendmicro.com.cn>
Acked-by: Jarkko Nikula <jarkko.nikula@linux.intel.com>
Signed-off-by: Mark Brown <broonie@kernel.org>