mfd: pm8008: Add driver for QCOM PM8008 PMIC

Qualcomm Technologies, Inc. PM8008 is a dedicated camera PMIC that
integrates all the necessary power management, housekeeping, and
interface support functions into a single IC. Its key features include
overtemperature protection, low-dropout linear regulators, GPIOs, and an
I2C interface.

Add an MFD driver to support it.

Signed-off-by: Guru Das Srinagesh <gurus@codeaurora.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>