net: napi: remove useless stack trace

Whenever a buggy NAPI driver returns more than its budget,
we emit a stack trace that is of no use, since it does not
tell which driver is buggy.

Instead, emit a message giving the function name, and a
descriptive message.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/core/dev.c

@@ -6683,7 +6683,9 @@ static int napi_poll(struct napi_struct *n, struct list_head *repoll)
 		trace_napi_poll(n, work, weight);
 	}
 
-	WARN_ON_ONCE(work > weight);
+	if (unlikely(work > weight))
+		pr_err_once("NAPI poll function %pS returned %d, exceeding its budget of %d.\n",
+			    n->poll, work, weight);
 
 	if (likely(work < weight))
 		goto out_unlock;