ASoC: ad193x: add support to ad1934

The AD1934 codec has no ADC feature. Hence it register mapping is slightly
different from the register mapping of other members of the AD193x family.

Some ASoC controls and widgets are related to the DAC feature so are not
relevant in the case of an AD1934 codec.

Signed-off-by: Cyrille Pitchen <cyrille.pitchen@atmel.com>
Acked-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Mark Brown <broonie@kernel.org>