Since the permanent generation has been removed, the card tables only needs two covering regions, so the argument max_covering_regions can be removed from the BarrierSet constructor, thus simplifying the code.
JDK-8083251The card tables only ever need two covering regions
JDK-8064876Remove all remnants of PermGen in CardTableRS
JDK-8065117Use GenCollectedHeap::_max_gens instead of BarrierSet::_max_covered_regions
JDK-8065137Remove unecessary generalizations in cardTableModRefBS.cpp