net: usbnet: constify the struct device_type usage

Since commit aed65af1 ("drivers: make device_type const"), the driver
core can properly handle constant struct device_type. Move the wlan_type
and wwan_type variables to be constant structures as well, placing it into
read-only memory which can not be modified at runtime.

Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Ricardo B. Marliere <ricardo@marliere.net>
Reviewed-by: Simon Horman <horms@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/usb/usbnet.c

@@ -1654,11 +1654,11 @@ static const struct net_device_ops usbnet_netdev_ops = {
 
 // precondition: never called in_interrupt
 
-static struct device_type wlan_type = {
+static const struct device_type wlan_type = {
 	.name	= "wlan",
 };
 
-static struct device_type wwan_type = {
+static const struct device_type wwan_type = {
 	.name	= "wwan",
 };