regulator: twl: fix twl6030 enable/disable

TWL6030 requires an additional register write to CFG_STATE register
to explicitly state that the regulator is in a certain state. Merely
associating the regulator with the group is not enough. Add the
required register field definitions and fix the handling for
TWL6030 enable/disable.

Signed-off-by: Nishanth Menon <nm@ti.com>
Signed-off-by: Saquib Herman <saquib@ti.com>
Acked-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: Liam Girdwood <lrg@vega.(none)>