mfd: wcd934x: Drop 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.

Fixes: 6ac7e4d7 ("mfd: wcd934x: Add support to wcd9340/wcd9341 codec")
Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>