mfd: intel_quark_i2c_gpio: Add Intel Quark X1000 I2C-GPIO MFD Driver

In Quark X1000, there's a single PCI device that provides both
an I2C controller and a GPIO controller. This MFD driver will
split the 2 devices for their respective drivers.

This patch is based on Josef Ahmad's initial work for Quark enabling.

Acked-by: Michael Turquette <mturquette@linaro.org>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Weike Chen <alvin.chen@intel.com>
Signed-off-by: Raymond Tan <raymond.tan@intel.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>