net: sched: cls_bpf: use bitwise & rather than logical && on gen_flags

Currently gen_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#1460305 ("Logical vs. bitwise operator")

Fixes: 3f7889c4 ("net: sched: cls_bpf: call block callbacks for offload)
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: David S. Miller <davem@davemloft.net>