staging: gdm724x: constantify the struct device_type usage

Since commit aed65af1cc2f ("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.

Signed-off-by: Ricardo B. Marliere <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/staging/gdm724x/gdm_lte.c

···
 	struct sock *sock;
 } lte_event;
 
-static struct device_type wwan_type = {
+static const struct device_type wwan_type = {
 	.name   = "wwan",
 };