ASoC: Move kfree(twl4030) to twl4030_soc_remove()

As we allocate memory for twl4030 in twl4030_codec_probe(),
twl4030_codec_remove() is a better place to free the memory.

Signed-off-by: Axel Lin <axel.lin@gmail.com>
Acked-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: Liam Girdwood <lrg@slimlogic.co.uk>