net: usb: Mark expected switch fall-throughs

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

Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/usb/r8152.c b/drivers/net/usb/r8152.c
index c08c0d6..a3e06a8 100644
--- a/drivers/net/usb/r8152.c
+++ b/drivers/net/usb/r8152.c
@@ -1376,6 +1376,7 @@ static void intr_callback(struct urb *urb)
 	case -ECONNRESET:	/* unlink */
 	case -ESHUTDOWN:
 		netif_device_detach(tp->netdev);
+		/* fall through */
 	case -ENOENT:
 	case -EPROTO:
 		netif_info(tp, intr, tp->netdev,
@@ -2741,6 +2742,7 @@ static void r8153b_ups_en(struct r8152 *tp, bool enable)
 			r8152_mdio_write(tp, MII_BMCR, data);
 
 			data = r8153_phy_status(tp, PHY_STAT_LAN_ON);
+			/* fall through */
 
 		default:
 			if (data != PHY_STAT_LAN_ON)