Hi,
Well, there is a way to do it in JavaScript, but as I understand you are looking for solution in Power BI.
We are considering making more configuration parameters available in Power BI, but in the meantime you can achieve the effect with a bit of hacking:
1) The visual.pbiviz file is actually a zip archive, so extract it to some folder with any unzip program.
2) There is a resources folder and a file in it. Open it in a text editor and find place that reads toolbar:{export:!1}
3) Replace it with toolbar:{logScale:!1,export:!1}
- adding another icon supressing flag
4) Compress the resources folder and package.json to a new archive. Rename it to visual.pbiviz and use in place of the original visual.pbiviz. The log/lin button will be gone.