Microphone / Headphones combo port does not work in BootCamp
Not sure if people are still having a problem with this as it's been almost a year, but I was running into this problem with my Mac mini 2014 with Windows 10 Home and Bootcamp v6.0.
  The sound card is Cirrus Logic CS4208 (AB 108), and I couldn't get Windows to recognize the mic on my headset which was designed for iPhone/Apple usage.

After not being able to find the driver for the CS4208 (AB 108) at a legitimate site on the net (results almost always required a 3rd party driver downloader - no thanks!), I went to Cirrus Logic's website and tried to search for another driver.  I was able to find CS4207 from their website, downloaded the zip file, and tried to update the CS4208 driver with files on this zip.  The driver was taken, and, after a restart, the microphone now showed up (even though it was still showing CS4208 AB 108).  It works!

I even rolled back the driver and updated again to confirm it works, and it sure does!  I also have another 2016 MBP that I would like to test.  Will update here after.

Here's a few screenshots before the driver update to CS4207:


And after updating the drivers and restart: