ASoC: TWL4030: Use reg_cache in twl4030_init_chip

Use the codec->reg_cache instead of the array directly
in twl4030_init_chip for setting the default values.

Signed-off-by: Peter Ujfalusi <peter.ujfalusi@nokia.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>