usb: cdc-wdm: Constify static struct wwan_port_ops

The only usage of wdm_wwan_port_ops is to pass its address to
wwan_create_port() which takes a pointer to const wwan_port_ops as
argument. Make it const to allow the compiler to put it in read-only
memory.
Signed-off-by: Rikard Falkeborn <rikard.falkeborn@gmail.com>
Acked-by: Oliver Neukum <oneukum@suse.com>
Link: https://lore.kernel.org/r/20210929194547.46954-3-rikard.falkeborn@gmail.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/class/cdc-wdm.c

@@ -911,7 +911,7 @@ static int wdm_wwan_port_tx(struct wwan_port *port, struct sk_buff *skb)
 	return rv;
 }
 
-static struct wwan_port_ops wdm_wwan_port_ops = {
+static const struct wwan_port_ops wdm_wwan_port_ops = {
 	.start = wdm_wwan_port_start,
 	.stop = wdm_wwan_port_stop,
 	.tx = wdm_wwan_port_tx,