ASoC: codecs: ad193x: Remove capture support for codecs without ADC

Some ad193x codecs don't have ADCs, so they have no capture capabilities.
This way, we can use this driver in multicodec cards.

Signed-off-by: Codrin Ciubotariu <codrin.ciubotariu@microchip.com>
Signed-off-by: Mark Brown <broonie@kernel.org>