ASoC: wcd: Update of IIR Gain value

Set IIR Gain after IIR mux setting to make sure the
gain has been properly applied on to the path. This is needed
to avoid sidetone mute during voice call.

Change-Id: I13af2c5e9583a597cf774b98b1d3f422a407dea0
CRs-Fixed: 600014
Signed-off-by: Sudheer Papothi <spapothi@codeaurora.org>