regulator: bd718XX use pickable ranges

Few regulators in BD71837 and BD71847 can output voltages from
different voltage ranges. Register interface is arranged so that
used range is selected by toggling bits which are not next to actual
voltage selection bits. Then the voltage inside selected range is
determined by voltage selection bits (as usual). Support BD71837
and BD71847 selectible range voltages using new pickable ranges
helpers.

Signed-off-by: Matti Vaittinen <matti.vaittinen@fi.rohmeurope.com>
Signed-off-by: Mark Brown <broonie@kernel.org>