ALSA: ASoC: TLV320AIC3X: Add support for digital microphone input

AIC33 and AIC34 codecs in TLV320AIC3x family support digital microphone
input. When enabled, the codec ADC takes bitstream input to low-pass
filter from GPIO2 instead of its own delta-sigma modulator while providing
oversampling clock through GPIO1.

Signed-off-by: Jarkko Nikula <jarkko.nikula@nokia.com>
Signed-off-by: Liam Girdwood <lg@opensource.wolfsonmicro.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Jaroslav Kysela <perex@perex.cz>