vlan: Mark expected switch fall-through

In preparation to enabling -Wimplicit-fallthrough, mark switch cases where we are expecting to fall through.

This patch fixes the following warning:

net/8021q/vlan_dev.c: In function ‘vlan_dev_ioctl’:
net/8021q/vlan_dev.c:374:6: warning: this statement may fall through [-Wimplicit-fallthrough=]
if (!net_eq(dev_net(dev), &init_net))

      ^

net/8021q/vlan_dev.c:376:2: note: here
case SIOCGMIIPHY:
^~~~

Warning level 3 was used: -Wimplicit-fallthrough=3

This patch is part of the ongoing efforts to enable -Wimplicit-fallthrough.

---
 net/8021q/vlan_dev.c | 1 +
 1 file changed, 1 insertion(+)

index 2a9a60733594..c546c4228075 100644
@@ -373,6 +373,7 @@ static int vlan_dev_ioctl(struct net_device *dev, struct ifreq *ifr, int cmd)
 	case SIOCSHWTSTAMP:
 		if (!net_eq(dev_net(dev), &init_net))
 			break;
+		/* fall through */
 	case SIOCGMIIPHY:
 	case SIOCGMIIREG:
 	case SIOCSMIIREG:

2.21.0

From: "Gustavo A. R. Silva" <[email protected]>
Date: Mon, 20 May 2019 09:51:05 -0500

Also applied to 'net', thanks.