mISDN: hfcmulti: don't call dev_kfree_skb/kfree_skb() under spin_lock_irqsave()

mISDN: hfcmulti: don't call dev_kfree_skb/kfree_skb() under spin_lock_irqsave()

[ Upstream commit 1232946cf522b8de9e398828bde325d7c41f29dd ]

It is not allowed to call kfree_skb() or consume_skb() from hardware
interrupt context or with hardware interrupts being disabled.

skb_queue_purge() is called under spin_lock_irqsave() in handle_dmsg()
and hfcm_l1callback(), kfree_skb() is called in them, to fix this, use
skb_queue_splice_init() to move the dch->squeue to a free queue, also
enqueue the tx_skb and rx_skb, at last calling __skb_queue_purge() to
free the SKBs afer unlock.

Fixes: ec89bda12621 ("Add mISDN HFC multiport driver")
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Reviewed-by: Alexander Duyck <alexanderduyck@fb.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>