This is mostly taken from the DragonflyBSD commit to the ig4 driver a4549657e6696a736bbe133ffe158bf59a0cd415 .
This adds support for Skylake and Kaby Lake to the ig4 driver.
I have tested this on a HP Chromebook 13 G1 with a Skylake CPU and Sunrise Point-LP I2C controller. I do not have any Atom or Haswell hardware to test against however, this should be tested to ensure that it hasn't regressed.