ASoC: adau1701: Implement sigmadsp safeload

The safeload feature allows to load up to 5 parameter memory registers
atomically. This is helpful for switching between e.g. filter settings
without causing any glitches.

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