net: hns: Fix a skb used after free bug

skb maybe freed in hns_nic_net_xmit_hw() and return NETDEV_TX_OK,
which cause hns_nic_net_xmit to use a freed skb.

BUG: KASAN: use-after-free in hns_nic_net_xmit_hw+0x62c/0x940...
	[17659.112635]      alloc_debug_processing+0x18c/0x1a0
	[17659.117208]      __slab_alloc+0x52c/0x560
	[17659.120909]      kmem_cache_alloc_node+0xac/0x2c0
	[17659.125309]      __alloc_skb+0x6c/0x260
	[17659.128837]      tcp_send_ack+0x8c/0x280
	[17659.132449]      __tcp_ack_snd_check+0x9c/0xf0
	[17659.136587]      tcp_rcv_established+0x5a4/0xa70
	[17659.140899]      tcp_v4_do_rcv+0x27c/0x620
	[17659.144687]      tcp_prequeue_process+0x108/0x170
	[17659.149085]      tcp_recvmsg+0x940/0x1020
	[17659.152787]      inet_recvmsg+0x124/0x180
	[17659.156488]      sock_recvmsg+0x64/0x80
	[17659.160012]      SyS_recvfrom+0xd8/0x180
	[17659.163626]      __sys_trace_return+0x0/0x4
	[17659.167506] INFO: Freed in kfree_skbmem+0xa0/0xb0 age=23 cpu=1 pid=13
	[17659.174000]      free_debug_processing+0x1...