This is a minor fix but helps to define dB ranges for volume controls.

Only DAC digital volume has full register value range from 0 to 127 but
ADC PGA gain and output stage volume controls don't.

For ADC PGA, maximum value is 119 and then it saturates to the same
gain value of 59.5 dB. For output stages, value 117 corresponds to -78.3 dB
and is muted for values 118 and above.
Signed-off-by: Jarkko Nikula <jarkko.nikula@nokia.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>