net: cavium: clean up return value check in cavium_ptp_probe

ptp_clock_register never return NULL, so no need check this
in cavium_ptp_probe.
Signed-off-by: NYueHaibing <yuehaibing@huawei.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/ethernet/cavium/common/cavium_ptp.c

@@ -277,10 +277,6 @@ static int cavium_ptp_probe(struct pci_dev *pdev,
 	writeq(clock_comp, clock->reg_base + PTP_CLOCK_COMP);
 
 	clock->ptp_clock = ptp_clock_register(&clock->ptp_info, dev);
-	if (!clock->ptp_clock) {
-		err = -ENODEV;
-		goto error_stop;
-	}
 	if (IS_ERR(clock->ptp_clock)) {
 		err = PTR_ERR(clock->ptp_clock);
 		goto error_stop;