net: wwan: core: 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 wwan_type
variable to be a constant structure 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>
Reviewed-by: Sergey Ryazanov <ryazanov.s.a@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/wwan/wwan_core.c

@@ -920,7 +920,7 @@ static int wwan_rtnl_validate(struct nlattr *tb[], struct nlattr *data[],
 	return 0;
 }
 
-static struct device_type wwan_type = { .name = "wwan" };
+static const struct device_type wwan_type = { .name = "wwan" };
 
 static struct net_device *wwan_rtnl_alloc(struct nlattr *tb[],
 					  const char *ifname,