zd1201: mark expected switch fall-through

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: Kalle Valo <kvalo@codeaurora.org>

drivers/net/wireless/zydas/zd1201.c

@@ -969,6 +969,7 @@ static int zd1201_set_mode(struct net_device *dev,
 			 */
 			zd1201_join(zd, "\0-*#\0", 5);
 			/* Put port in pIBSS */
+			/* Fall through */
 		case 8: /* No pseudo-IBSS in wireless extensions (yet) */
 			porttype = ZD1201_PORTTYPE_PSEUDOIBSS;
 			break;