ASoC: msm8x16-wcd: disable mclk enable flag during device down

MCLK enable flag has to be made false during device down in SSR
this will make sure that in device up before accesing digital
core the MCLK is enabled.

CRs-Fixed: 723134
Change-Id: I3aa7f7cf3a196803bd54bdafcbab679ba827ca92
Signed-off-by: Santosh Mardi <gsantosh@codeaurora.org>