ASoC: wcd-mbhc: Disconnect ANC from RX chain during plug removal

Disconnect ANC from RX when headphone plug is removed from the jack
to prevent any audible pop noise.

Change-Id: I7a3f6e876f8560580965762c7393c83833ef3b47
Signed-off-by: Meng Wang <mwang@codeaurora.org>