netpoll: netpoll_send_skb() returns transmit status

mainline inclusion
from mainline-v5.11-rc2
commit 1ddabdfa
category: bugfix
bugzilla: 46921
CVE: NA

-------------------

Some callers want to know if the packet has been sent or
dropped, to inform upper stacks.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Aichun Li <liaichun@huawei.com>
Reviewed-by: Yue Haibing <yuehaibing@huawei.com>
Reviewed-by: wangxiaopeng <wangxiaopeng7@huawei.com>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Signed-off-by: Cheng Jian <cj.chengjian@huawei.com>