Oh, also edit /etc/modules and add:
# /etc/modules: kernel modules to load at boot time.
#
# This file contains the names of kernel modules that should be loaded
# at boot time, one per line. Lines beginning with "#" are ignored.
i2c-dev
The mics are using i2c
You could also enable it through raspi-config I think.
I updated the kernel like this:
#Update kernel version to 4.9
sudo apt-get update
sudo apt-get upgrade
sudo apt-get install rpi-update
sudo rpi-update
sudo reboot
But if your sound is working, it should use the right kernel already