net: ena: Fix using plain integer as NULL pointer in ena_init_napi_in_range

Fix sparse build warning:

drivers/net/ethernet/amazon/ena/ena_netdev.c:2193:34: warning:
 Using plain integer as NULL pointer
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Wang Hai <wanghai38@huawei.com>
Suggested-by: Joe Perches <joe@perches.com>
Acked-by: Shay Agroskin <shayagr@amazon.com>
Acked-by: Shay Agroskin <shayagr@amazon.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/amazon/ena/ena_netdev.c

@@ -2190,14 +2190,13 @@ static void ena_del_napi_in_range(struct ena_adapter *adapter,
 static void ena_init_napi_in_range(struct ena_adapter *adapter,
 				   int first_index, int count)
 {
-	struct ena_napi *napi = {0};
 	int i;
 
 	for (i = first_index; i < first_index + count; i++) {
-		napi = &adapter->ena_napi[i];
+		struct ena_napi *napi = &adapter->ena_napi[i];
 
 		netif_napi_add(adapter->netdev,
-			       &adapter->ena_napi[i].napi,
+			       &napi->napi,
 			       ENA_IS_XDP_INDEX(adapter, i) ? ena_xdp_io_poll : ena_io_poll,
 			       ENA_NAPI_BUDGET);