net: stmmac: Fix channel lock initialization

Commit 0366f7e0 ("net: stmmac: add ethtool support for get/set
channels") refactored channel initialization, but during that operation,
the spinlock initialization got lost. Fix this. This fixes the following
lockdep warning:

meson8b-dwmac ff3f0000.ethernet eth0: Link is Up - 1Gbps/Full - flow control off
INFO: trying to register non-static key.
the code is fine but needs lockdep annotation.
turning off the locking correctness validator.
CPU: 1 PID: 331 Comm: kworker/1:2H Not tainted 5.9.0-rc3+ #1858
Hardware name: Hardkernel ODROID-N2 (DT)
Workqueue: kblockd blk_mq_run_work_fn
Call trace:
 dump_backtrace+0x0/0x1d0
 show_stack+0x14/0x20
 dump_stack+0xe8/0x154
 register_lock_class+0x58c/0x590
 __lock_acquire+0x7c/0x1790
 lock_acquire+0xf4/0x440
 _raw_spin_lock_irqsave+0x80/0xb0
 stmmac_tx_timer+0x4c/0xb0 [stmmac]
 call_timer_fn+0xc4/0x3e8
 run_timer_softirq+0x2b8/0x6c0
 efi_header_end+0x114/0x5f8
 irq_exit+0x104/0x110
 __handle_domain_irq+0x60/0xb8
 gic_handle_irq+0x58/0xb0
 el1_irq+0xbc/0x180
 _raw_spin_unlock_irqrestore+0x48/0x90
 mmc_blk_rw_wait+0x70/0x160
 mmc_blk_mq_issue_rq+0x510/0x830
 mmc_mq_queue_rq+0x13c/0x278
 blk_mq_dispatch_rq_list+0x2a0/0x698
 __blk_mq_do_dispatch_sched+0x254/0x288
 __blk_mq_sched_dispatch_requests+0x190/0x1d8
 blk_mq_sched_dispatch_requests+0x34/0x70
 __blk_mq_run_hw_queue+0xcc/0x148
 blk_mq_run_work_fn+0x20/0x28
 process_one_work+0x2a8/0x718
 worker_thread+0x48/0x460
 kthread+0x134/0x160
 ret_from_fork+0x10/0x1c

Fixes: 0366f7e0 ("net: stmmac: add ethtool support for get/set channels")
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Link: https://lore.kernel.org/r/20201029185011.4749-1-m.szyprowski@samsung.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/ethernet/stmicro/stmmac/stmmac_main.c

@@ -4757,6 +4757,7 @@ static void stmmac_napi_add(struct net_device *dev)
 
 		ch->priv_data = priv;
 		ch->index = queue;
+		spin_lock_init(&ch->lock);
 
 		if (queue < priv->plat->rx_queues_to_use) {
 			netif_napi_add(dev, &ch->rx_napi, stmmac_napi_poll_rx,