driver: net: ldpaa: Update priv->phydev after free()

Even after memory free of phydev, priv is still pointing to the
obsolete address.
So update priv->phydev as NULL after memory free.
Signed-off-by: NPrabhakar Kushwaha <prabhakar.kushwaha@nxp.com>
Signed-off-by: NAshish Kumar <Ashish.Kumar@nxp.com>
Acked-by: NJoe Hershberger <joe.hershberger@ni.com>

drivers/net/ldpaa_eth/ldpaa_eth.c

@@ -587,8 +587,10 @@ static void ldpaa_eth_stop(struct eth_device *net_dev)
 #ifdef CONFIG_PHYLIB
 	if (priv->phydev && bus != NULL)
 		phy_shutdown(priv->phydev);
-	else
+	else {
 		free(priv->phydev);
+		priv->phydev = NULL;
+	}
 #endif
 
 	ldpaa_dpbp_free();