net: sched: cls_u32: use bitwise & rather than logical && on n->flags

Currently n->flags is being operated on by a logical && operator rather
than a bitwise & operator. This looks incorrect as these should be bit
flag operations. Fix this.

Detected by CoverityScan, CID#1460398 ("Logical vs. bitwise operator")

Fixes: 245dc512 ("net: sched: cls_u32: call block callbacks for offload")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: David S. Miller <davem@davemloft.net>