ASoC: Intel: byt-rt5640: Enable DMIC interface for default DAPM route

It turned out DMIC interface wasn't enabled/disabled runtime for active
DMIC route in the rt5640 codec driver anymore after commit
71d97a79 ("ASoC: rt5640: Use the platform data for DMIC settings").

Since DMIC interface must be enabled explicitly either by passing platform
data to rt5640 codec driver or by calling new rt5640_dmic_enable() this
patch adds a DMI quirk flag that is used to conditionally enable DMIC
interface during sound card init time.

Signed-off-by: Jarkko Nikula <jarkko.nikula@linux.intel.com>
Signed-off-by: Mark Brown <broonie@kernel.org>