Currently (Clover 3.2.0) there is no such option in the maven-clover2-plugin. There is a feature request reported, so you can track a progress here: https://jira.atlassian.com/browse/CLOV-1173 - it's on the road map, scheduled for year 2014.
As a workaround you could use a custom report descriptor. See
https://docs.atlassian.com/maven-clover2-plugin/latest/clover-mojo.html#reportDescriptor
and
https://confluence.atlassian.com/display/CLOVER/Creating+custom+reports