net: aquantia: fix return value check in aq_ptp_init()

Function ptp_clock_register() returns ERR_PTR() and never returns
NULL. The NULL test should be removed.
Signed-off-by: NWei Yongjun <weiyongjun1@huawei.com>
Acked-by: NIgor Russkikh <irusskikh@marvell.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/ethernet/aquantia/atlantic/aq_ptp.c

@@ -1207,7 +1207,7 @@ int aq_ptp_init(struct aq_nic_s *aq_nic, unsigned int idx_vec)
 	aq_ptp->ptp_info = aq_ptp_clock;
 	aq_ptp_gpio_init(&aq_ptp->ptp_info, &mbox.info);
 	clock = ptp_clock_register(&aq_ptp->ptp_info, &aq_nic->ndev->dev);
-	if (!clock || IS_ERR(clock)) {
+	if (IS_ERR(clock)) {
 		netdev_err(aq_nic->ndev, "ptp_clock_register failed\n");
 		err = PTR_ERR(clock);
 		goto err_exit;