net: mhi_net: make mhi_wwan_ops static

This symbol is not used outside of net.c, so marks it static.

Fix the following sparse warning:

drivers/net/mhi/net.c:385:23: warning: symbol 'mhi_wwan_ops' was not
declared. Should it be static?
Reported-by: Abaci Robot <abaci@linux.alibaba.com>
Signed-off-by: Jiapeng Chong <jiapeng.chong@linux.alibaba.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/mhi/net.c

@@ -382,7 +382,7 @@ static void mhi_net_dellink(void *ctxt, struct net_device *ndev,
 	dev_set_drvdata(&mhi_dev->dev, NULL);
 }
 
-const struct wwan_ops mhi_wwan_ops = {
+static const struct wwan_ops mhi_wwan_ops = {
 	.owner = THIS_MODULE,
 	.priv_size = sizeof(struct mhi_net_dev),
 	.setup = mhi_net_setup,