ASoC: wcd9304: Fix IIR filter controls

Add IIR2 filter interface for the wcd9304 codec.
Control the two 5 band IIR filters in the audio
codec through mixer controls. Enable individual
IIR filter bands and set band coefficients.

Change the IIR filter code to use snd_soc_write
instead of snd_soc_update_bits. If update bits
is used the IIR registers may not be correctly
updated.

Change-Id: I92fc147641e9eb270d8176f20445371fe5cc2f92
Signed-off-by: Asish Bhattacharya <asishb@codeaurora.org>