The recent fix for adding rwsem nesting annotation was using the given
"hop" argument as the lock subclass key. Although the idea itself
works, it may trigger a kernel warning like:
BUG: looking up invalid subclass: 8
....
since the lockdep has a smaller number of subclasses (8) than we
currently allow for the hops there (10).
The current definition is merely a sanity check for avoiding the too
deep delivery paths, and the 8 hops are already enough. So, as a
quick fix, just follow the max hops as same as the max lockdep
subclasses.