ASoC: wcd9335: add TXFE power mode mixer control

WCD9335 has different power mode for analog mic inputs
The design is that two consecutive microphones share
same power mode. Along with power mode on analog mic
register, corresponding mode would have to be set on
decimator when it is connected to analog microphone.

Change-Id: Ib16ffaa4cb4a58deef35c1f2c21f42418c32de19
Signed-off-by: Patrick Lai <plai@codeaurora.org>
Signed-off-by: Phani Kumar Uppalapati <phaniu@codeaurora.org>