net: phy: micrel: Fix warn: passing zero to PTR_ERR

Handle the NULL pointer case

Fixes New smatch warnings:
drivers/net/phy/micrel.c:2613 lan8814_ptp_probe_once() warn: passing zero to 'PTR_ERR'

vim +/PTR_ERR +2613 drivers/net/phy/micrel.c
Reported-by: kernel test robot <lkp@intel.com>
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: Alexander Duyck <alexanderduyck@fb.com>
Signed-off-by: Divya Koppera <Divya.Koppera@microchip.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/phy/micrel.c

@@ -3008,10 +3008,6 @@ static int lan8814_ptp_probe_once(struct phy_device *phydev)
 {
 	struct lan8814_shared_priv *shared = phydev->shared->priv;
 
-	if (!IS_ENABLED(CONFIG_PTP_1588_CLOCK) ||
-	    !IS_ENABLED(CONFIG_NETWORK_PHY_TIMESTAMPING))
-		return 0;
-
 	/* Initialise shared lock for clock*/
 	mutex_init(&shared->shared_lock);
 
@@ -3031,12 +3027,16 @@ static int lan8814_ptp_probe_once(struct phy_device *phydev)
 
 	shared->ptp_clock = ptp_clock_register(&shared->ptp_clock_info,
 					       &phydev->mdio.dev);
-	if (IS_ERR_OR_NULL(shared->ptp_clock)) {
+	if (IS_ERR(shared->ptp_clock)) {
 		phydev_err(phydev, "ptp_clock_register failed %lu\n",
 			   PTR_ERR(shared->ptp_clock));
 		return -EINVAL;
 	}
 
+	/* Check if PHC support is missing at the configuration level */
+	if (!shared->ptp_clock)
+		return 0;
+
 	phydev_dbg(phydev, "successfully registered ptp clock\n");
 
 	shared->phydev = phydev;