ASoC: max9867: keep ADCs and DACs always on

Updating power management register requires toggling the shutdown
bit otherwise it causes unexpected behavior of the codec.
However, toggling the shutdown bit results in loud speaker crackling.
Setup the power management register only at startup to avoid that.

Signed-off-by: Pavel Dobias <dobias@2n.cz>
Link: https://lore.kernel.org/r/20200522142957.18364-3-dobias@2n.cz
Signed-off-by: Mark Brown <broonie@kernel.org>