ASoC: dapm - Refactor widget IO functions in preparation for platform widgets.

This time with soc_widget_update_bits reflecting recent soc_update_bits changes.

Currently widget IO is tightly coupled to the CODEC drivers. Future platform DSP
devices have mixer components that can alter power usage and hence require full
DAPM support.

This provides a generic widget IO operation wrapper in preparation for
future patches that implement platform driver DAPM.

Signed-off-by: Liam Girdwood <lrg@ti.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>