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: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/net/cls_cgroup.h b/include/net/cls_cgroup.h
index 6cf4486..726cc35 100644
--- a/include/net/cls_cgroup.h
+++ b/include/net/cls_cgroup.h
@@ -39,7 +39,7 @@
 static inline u32 task_cls_classid(struct task_struct *p)
 {
 	int id;
-	u32 classid;
+	u32 classid = 0;
 
 	if (in_interrupt())
 		return 0;