regulator: ab8500: Let regulator core handle the case no delay for setting new...

regulator: ab8500: Let regulator core handle the case no delay for setting new voltage if regulator is off

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