net:dsa: check for EPROBE_DEFER from dsa_dst_parse()

Since there can be multiple dsa switches stacked together but
not all of devicetree nodes available at the time of calling
dsa_dst_parse(), EPROBE_DEFER can be returned by it. When this
happens, only the last dsa switch has to be deleted by
dsa_dst_del_ds(), but not the whole list, because next time linux
cames back to this function it will try to add only the last dsa
switch which returned EPROBE_DEFER.
Signed-off-by: Volodymyr Bendiuga <volodymyr.bendiuga@gmail.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/dsa/dsa2.c

@@ -647,8 +647,14 @@ static int _dsa_register_switch(struct dsa_switch *ds, struct device_node *np)
 	}
 
 	err = dsa_dst_parse(dst);
-	if (err)
+	if (err) {
+		if (err == -EPROBE_DEFER) {
+			dsa_dst_del_ds(dst, ds, ds->index);
+			return err;
+		}
+
 		goto out_del_dst;
+	}
 
 	err = dsa_dst_apply(dst);
 	if (err) {