ASoC: rt5682: Add a property for DMIC clock rate

The patch adds a property for DMIC clock rate (hz) and changes the
default to the common optimize DMIC clock rate.

Signed-off-by: Oder Chiou <oder_chiou@realtek.com>
Link: https://lore.kernel.org/r/20200323082547.7898-1-oder_chiou@realtek.com


Signed-off-by: Mark Brown <broonie@kernel.org>