regulators: Clean out unused code in ab8500 regulators

The find_regulator function was unused so it has been removed. The
ab8500 pointer in the regulator info structure was unused and so it
has also been removed.

Signed-off-by: Bengt Jonsson <bengt.g.jonsson@stericsson.com>
Acked-by: Linus Walleij <linus.walleij@stericsson.com>
Acked-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: Liam Girdwood <lrg@slimlogic.co.uk>