regulator: lp872x: initialize the DVS mode

 The platform specific configuration(general_config) is optional.
 However, the DVS settings should be configured explicitly while
 loading the driver.
 This patch enables configuring the default DVS mode even though
 the platform data is not defined.

Signed-off-by: Milo(Woogyom) Kim <milo.kim@ti.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>