mfd: intel_quark_i2c_gpio: Add support for SIMATIC IOT2000 platform

The SIMATIC IOT2020 and IOT2040 are derived from the Galileo Gen2 board
and share its I2C frequency.

Signed-off-by: Sascha Weisenberger <sascha.weisenberger@siemens.com>
Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>