CURRENT (r298939): kernelbuild failure: _cpuset.h:50:1: error: use of undeclared identifier 'NBBY'

CURRENT (r298939) kernelbuild fails due to the error shown below:

[...]
In file included from /usr/src/lib/libdevctl/devctl.c:31:
In file included from /usr/obj/usr/src/tmp/usr/include/sys/bus.h:35:
/usr/obj/usr/src/tmp/usr/include/sys/_cpuset.h:50:1: error: use of undeclared identifier
'NBBY' /usr/obj/usr/src/tmp/usr/include/sys/_bitset.h:52:24: note: expanded from macro
'BITSET_DEFINE' long    __bits[__bitset_words((_s))];                           \
                       ^
/usr/obj/usr/src/tmp/usr/include/sys/_bitset.h:41:41: note: expanded from macro
'__bitset_words' #define __bitset_words(_s)      (howmany(_s, _BITSET_BITS))