Hello Ari Sinisalo,
You may search through the available recipes in Yocto by using the following command:
bitbake -s | grep opencv
There is a package for opencv (and opencv-samples) but in the L4.1.15 BSP Release this is version 2.4.
The Krogoth branch from the Community BSP does support OpenCV 3.1.
You may add the support for more recent OpenCV versions manually though. There are some documents on the communities that may be of help, such as the following: