configs: msmnile: update headset codec tx gain

Loopback test fails because headset codec tx gain is
higher than expected. Headset tx codec gain is wrongly
increased for new digital mics which are only used for
handset/speaker mics.

Reduce headset codec tx gain to same level as 845.

CRs-Fixed: 2280116
Change-Id: I0ce03f2d7cacff1d0f5c2b05c7bb2ad2b0a523ec