pkt_sched: Fix warning false positives.

pkt_sched: Fix warning false positives.

commit f54ba7798848ce1385a71b36a2c997422c82220a upstream.

GCC refuses to recognize that all error control flows do in fact
set err to something.

Add an explicit initialization to shut it up.

net/sched/sch_drr.c: In function ‘drr_enqueue’:
net/sched/sch_drr.c:359:11: warning: ‘err’ may be used uninitialized in this function [-Wmaybe-uninitialized]
net/sched/sch_qfq.c: In function ‘qfq_enqueue’:
net/sched/sch_qfq.c:885:11: warning: ‘err’ may be used uninitialized in this function [-Wmaybe-uninitialized]

Signed-off-by: David S. Miller <davem@davemloft.net>
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>