ASoC: codecs: ad193x: Add runtime support for DSP_A and I2S modes

The driver only supports DPS_A for DAC, which is configured at probe.
This patch adds support for DSP_A and I2S modes by using the set_fmt()
callback.

A trivial break is also removed from a case's default branch.

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