ASoC: JZ4770: codec: Cleanups

Most importantly make sure we call snd_soc_codec_set_cache_io(); for
some reason that is currently not strictly needed, but that is a very
fragile situation.

Rename codec probe/remove functions similar to other drivers.

Made struct static since it wasn't used outside this module.
ASoC: JZ4770: codec: Support different microphone setups via pdata

The board determines how many microphones there are and whether they
are mono or stereo, so put that information in platform data instead
of having user-operated controls for it.