cls_cgroup: Initialise classid when module is absent

When the cls_cgroup module is not loaded, task_cls_classid will
return an uninitialised classid instead of zero.
Reported-by: NStephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: NHerbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

include/net/cls_cgroup.h

@@ -39,7 +39,7 @@ extern int net_cls_subsys_id;
 static inline u32 task_cls_classid(struct task_struct *p)
 {
 	int id;
-	u32 classid;
+	u32 classid = 0;
 
 	if (in_interrupt())
 		return 0;