regulator: ab3100: add missing voltage table

The conversion to voltage tables in

commit a3beb742


"regulator: ab3100: Use regulator_list_voltage_table()"

missed to add the voltage table to the buck. Fix this and
it works like a charm.

Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Acked-by: Axel Lin <axel.lin@gmail.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>