mfd/ASoC: Convert WM8994 driver to use regmap patches

Early revisions of several of the WM8994 variants have register updates
to improve performance. Move these over to using the regmap patch system
instead of open coding them in the audio driver. Since the regmap init
is done by the MFD the code is moved there.

Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Acked-by: Samuel Ortiz <sameo@linux.intel.com>