this warning:

  net/sched/sch_hfsc.c: In function ‘hfsc_enqueue’:
  net/sched/sch_hfsc.c:1577: warning: ‘err’ may be used uninitialized in this function

triggers because GCC does not recognize the (correct) error flow
between hfsc_classify(), 'cl' and 'err'.

Annotate it.
Signed-off-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>