MINOR: debug: check the match count in __BUG_ON_ONCE() and not in complain()

MINOR: debug: check the match count in __BUG_ON_ONCE() and not in complain()

The fix in commit 7a78d6c600 ("BUG/MINOR: debug: only dump the trace once
in __BUG_ON_ONCE()") warned that it's not strictly atomic, but we could
do better and take this opportunity for cleaning the code: use a fetch-add
in __BUG_ON_ONCE() and pass NULL to complain(), which thus no longer has
any call place requiring it to check a counter. This only very slightly
inflates the code (~138B) since each BUG_ON_ONCE() now has to load 1,
xadd(), check the return value instead of leaving it to complain(), but
this is totally marginal compared to the benefits.

This can even be backported where the fix above is backported if needed.