mfd: Add support for Intel Sunrisepoint LPSS devices

The new coming Intel platforms such as Skylake will contain Sunrisepoint PCH.
The main difference to the previous platforms is that the LPSS devices are
compound devices where usually main (SPI, HSUART, or I2C) and DMA IPs are
present.

This patch brings the driver for such devices found on Sunrisepoint PCH.

Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>