ASoC: wcd9310: add IIR1 input volume controls

There are four inputs to IIR1. Gain range is between -84
to +40 DB for all 4 inputs. These gain controls would
serve mostly for sidetone gain control purpose.

CRs-fixed: 309261
Change-Id: I44141b07f764f75efc33d3badebb331d0322cdb2
Signed-off-by: Patrick Lai <plai@codeaurora.org>