ASoC: msm8996: Add support for VI feedback channel config

VI feedback path is used in speaker protection and for
each speaker that is present on the board it needs 2 channels,
one for voltage (V) and one for current (I). Add support to
configure the number of channels based on whether board has
mono or stereo speakers.

Change-Id: I2e68d5548cffd1aa60f48d99b3cfd03fd07fb631
Signed-off-by: Phani Kumar Uppalapati <phaniu@codeaurora.org>