ARM: S3C64XX: Use IN4 DC measurement mode on Tobermory

The WM8962 on Tobermory has one of the IN4 inputs connected for DC
measurement. Tell the driver it can optimise for this mode.

Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Acked-by: Kukjin Kim <kgene.kim@samsung.com>