ASoC: wcd: Update of IIR Gain value

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

Change-Id: I26bb057a65e29ea69b437d9f89674b5a3f35235e
CRs-Fixed: 600014
Signed-off-by: Laxminath Kasam <lkasam@codeaurora.org>