regulator: Enable the ab8500 for Device Tree

Here we setup the ab8500 regulator driver for DT. We first do
this in the normal way, by providing a match structure during
initialisation, but then we provide information so that
whilst probing we can use existing data structures to do DT
look-ups.

Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>