ASoC: wcd938x: Resolve noise during dmic record

Channel rate is set same as clk rate resulting in 
noise during dmic record. Set channel rate for dmic
based on port params not clk rate to resolve noise.

Change-Id: Ie65c72be5ed3719a1204f800571329ea5b5985fc
Signed-off-by: Vatsal Bucha <vbucha@codeaurora.org>