ASoC: pcm512x: Add 'Analogue' prefix to analogue volume controls

This is to ensure that 'alsactl restore' does not apply default
initialisation as the chip reset defaults are preferred.

Signed-off-by: Howard Mitchell <hm@hmbedded.co.uk>
Signed-off-by: Mark Brown <broonie@kernel.org>
Cc: stable@vger.kernel.org