ASoC: wcd9310: Turn off DMIC clk when both DMICs in the pair are off.

Digital Mic inputs on Tabla comes in Pairs. The DMICs in a pair share
same clock. So even if one of the DMIC in pair is powered down clk should
not be turned off if the other DMIC in pair is still active.

CRs-Fixed: 357684
Change-Id: I9ddc9d88cdd8f81e8fa7a9ea7899bc8c324cb94e
Signed-off-by: Kiran Kandi <kkandi@codeaurora.org>