ASoC: sta32x: preserve coefficient RAM

The coefficient RAM must be saved in a shadow so it can
be restored when the codec is powered on using
regulator_bulk_enable().

Signed-off-by: Johannes Stezenbach <js@sig21.net>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Cc: stable@vger.kernel.org