ASoC: wm8962: Optimise power consumption for IN4 DC measurement usage

When the hardware is configured with one or both of the IN4 inputs used
for DC measurement (with no DC blocking capacitor connected) then we can
improve power consumption slightly in idle modes by applying a register
write sequence. Provide platform data to enable this, implemented using
a regmap patch.

Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>