net/smc: use GFP_ATOMIC allocation in smc_pnet_add_eth()

My last patch moved the netdev_tracker_alloc() call to a section
protected by a write_lock().

I should have replaced GFP_KERNEL with GFP_ATOMIC to avoid the infamous:

BUG: sleeping function called from invalid context at include/linux/sched/mm.h:256

Fixes: 28f92221 ("net/smc: fix ref_tracker issue in smc_pnet_add()")
Signed-off-by: NEric Dumazet <edumazet@google.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/smc/smc_pnet.c

@@ -382,7 +382,7 @@ static int smc_pnet_add_eth(struct smc_pnettable *pnettable, struct net *net,
 		if (ndev) {
 			new_pe->ndev = ndev;
 			netdev_tracker_alloc(ndev, &new_pe->dev_tracker,
-					     GFP_KERNEL);
+					     GFP_ATOMIC);
 		}
 		list_add_tail(&new_pe->list, &pnettable->pnetlist);
 		write_unlock(&pnettable->lock);