ASoC: adau1761: Fix input PGA volume

For the input PGA to work correctly the ALC clock needs to be active.
Otherwise volume changes are not applied.

Fixes: dab464b6 ("ASoC: Add ADAU1361/ADAU1761 audio CODEC support")
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Cc: stable@vger.kernel.org
Signed-off-by: Mark Brown <broonie@kernel.org>