Fix a potential NULL pointer dereference in free_shared_mem() in drivers/net/s2io.c

This patch fixes a potential null dereference bug where we dereference
nic before a null check. This patch simply moves the dereferencing
after the null check.

Signed-off-by: Micah Gruber < micah.gruber@gmail.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>

drivers/net/s2io.c

@@ -796,12 +796,14 @@ static void free_shared_mem(struct s2io_nic *nic)
 	struct mac_info *mac_control;
 	struct config_param *config;
 	int lst_size, lst_per_page;
-	struct net_device *dev = nic->dev;
+	struct net_device *dev;
 	int page_num = 0;
 
 	if (!nic)
 		return;
 
+	dev = nic->dev;
+
 	mac_control = &nic->mac_control;
 	config = &nic->config;