ASoC: TWL4030: Module unloading fix

The module unloading path had several problems:
- it freed up the private structure twice
- it freed up the codec structure, which was allocated as part
  of the private structure
- it did not freed up the reg_cache
- it did not unregistered the dais and the codec

Signed-off-by: Peter Ujfalusi <peter.ujfalusi@nokia.com>
Acked-by: Liam Girdwood <lrg@slimlogic.co.uk>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>