regulator: wm8994: Provide default init data

Almost all systems use the regulators on the WM8994 series devices to
provide DCVDD and AVDD1 so if no init data is supplied then set up the
supplies for the user. This simplifies integration of the device into
systems, especially when device tree is supported.

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