bpf: clear sender_cpu before xmit

Similar to commit c29390c6 ("xps: must clear sender_cpu before forwarding")
the skb->sender_cpu needs to be cleared before xmit.

Fixes: 3896d655 ("bpf: introduce bpf_clone_redirect() helper")
Signed-off-by: Alexei Starovoitov <ast@plumgrid.com>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: David S. Miller <davem@davemloft.net>