ASoC: wcd9306: Add DMIC sample rate support to wcd9306

Add the capability to read DMIC sample rate from device
tree file to wcd9306. This enables different sample rates
without changing the codec driver.

CRs-fixed: 542737
Change-Id: I436df2114f9f19cb6a17c8e700df2654deede7e1
Signed-off-by: Damir Didjusto <damird@codeaurora.org>