regulator: palmas: Add DT support

Add DT support to palmas regulator. This involved a little change to
the platform data structure. Regulator information can now come from
platform data or DT.

Signed-off-by: Graeme Gregory <gg@slimlogic.co.uk>
Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>