mfd: DT bindings for the palmas family MFD

Add the various binding files for the palmas family of chips. There is a
top level MFD binding then a seperate binding for regulators IP blocks on chips.

Signed-off-by: Graeme Gregory <gg@slimlogic.co.uk>
Signed-off-by: J Keerthy <j-keerthy@ti.com>
Signed-off-by: Ian Lartey <ian@slimlogic.co.uk>
Reviewed-by: Stephen Warren <swarren@nvidia.com>
Signed-off-by: Grant Likely <grant.likely@linaro.org>