ASoC: ad193x: Don't power down DAC in CODEC probe

The DAC powerdown bit is managed by DAPM. Manually powering down the DAC in
the CODEC probe function may cause unnecessary power state transitions which
can lead to click and pop noises.

So leave the DAC powerdown bit in its default poweron-reset state and let
DAPM do all the management.

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Mark Brown <broonie@kernel.org>