MFC: r317982

MFC: r317982

- Also outside of the KOBJOPLOOKUP macro - which in turn is used by
  the code auto-generated for *.m - kobj_lookup_method(9) is useful;
  for example in back-ends or base class device drivers in order to
  determine whether a default method has been overridden. Thus, allow
  for the kobj_method_t pointer argument - used by KOBJOPLOOKUP in
  order to update the cache entry - of kobj_lookup_method(9), to be
  NULL. Actually, that pointer is redundant as it's just set to the
  same kobj_method_t that the kobj_lookup_method(9) function returns
  in the first place, but probably it serves to reduce the number of
  instructions generated for KOBJOPLOOKUP.
- For the same reason, move updating kobj_lookup_{hits,misses} (if
  KOBJ_STATS is defined) from kobj_lookup_method(9) to KOBJOPLOOKUP.
  As a side-effect, this gets rid of the convoluted approach of always
  incrementing kobj_lookup_hits in KOBJOPLOOKUP and then in case of
  a cache miss, decrementing it in kobj_lookup_method(9) again.

git-svn-id: svn://svn.freebsd.org/base/stable/10@318275 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f