All callers of devfs_find_and_unregister() pass 0 in 6th argument.  All
uses of that function either pass 0 in 3rd and 4th argument (in which
case the 5th is ignored) or pass the existing pathname in the 2nd (in
which case 3rd, 4th and 5th are ignored).  In all cases the first
argument can be trivially made NULL.

devfs_find_and_unregister() is left as-is.  All existing callers
converted to new helper - devfs_remove(pathname).  Said beast does
equivalent of devfs_find_and_unregister(NULL, pathname, 0, 0, 0, 0);