mfd: Add LP87565 PMIC support

The LP87565 chip is a power management IC for Portable Navigation Systems
and Tablet Computing devices. It contains the following components:

        - Configurable Bucks(Single and multi-phase).
        - Configurable General Purpose Output Signals (GPO).

The LP87565-Q1 variant device uses two 2-phase outputs configuration,
Buck0 is master for Buck0/1 output and Buck2 is master for Buck2/3
output.

Signed-off-by: Keerthy <j-keerthy@ti.com>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>