net: dsa: fix dereference on ds->dev before null check error

Currently ds->dev is dereferenced on the assignments of pdata and
np before ds->dev is null checked, hence there is a potential null
pointer dereference on ds->dev.  Fix this by assigning pdata and
np after the ds->dev null pointer sanity check.

Addresses-Coverity: ("Dereference before null check")
Fixes: 7e99e347 ("net: dsa: remove dsa_switch_alloc helper")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Reported-by: kbuild test robot <lkp@intel.com>
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: Vivien Didelot <vivien.didelot@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/dsa/dsa2.c

@@ -842,13 +842,16 @@ static int dsa_switch_add(struct dsa_switch *ds)
 
 static int dsa_switch_probe(struct dsa_switch *ds)
 {
-	struct dsa_chip_data *pdata = ds->dev->platform_data;
-	struct device_node *np = ds->dev->of_node;
+	struct dsa_chip_data *pdata;
+	struct device_node *np;
 	int err;
 
 	if (!ds->dev)
 		return -ENODEV;
 
+	pdata = ds->dev->platform_data;
+	np = ds->dev->of_node;
+
 	if (!ds->num_ports)
 		return -EINVAL;