isdn: mark expected switch fall-throughs

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

Warning level 2 was used: -Wimplicit-fallthrough=2

Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/isdn/hardware/mISDN/mISDNisar.c

@@ -972,6 +972,7 @@ isar_pump_statev_fax(struct isar_ch *ch, u8 devt) {
 				break;
 			case PCTRL_CMD_FTM:
 				p1 = 2;
+				/* fall through */
 			case PCTRL_CMD_FTH:
 				send_mbox(ch->is, dps | ISAR_HIS_PUMPCTRL,
 					  PCTRL_CMD_SILON, 1, &p1);
@@ -1177,6 +1178,7 @@ setup_pump(struct isar_ch *ch) {
 			send_mbox(ch->is, dps | ISAR_HIS_PUMPCFG,
 				  PMOD_DTMF, 1, param);
 		}
+		/* fall through */
 	case ISDN_P_B_MODEM_ASYNC:
 		ctrl = PMOD_DATAMODEM;
 		if (test_bit(FLG_ORIGIN, &ch->bch.Flags)) {
@@ -1268,6 +1270,7 @@ setup_iom2(struct isar_ch *ch) {
 	case ISDN_P_B_MODEM_ASYNC:
 	case ISDN_P_B_T30_FAX:
 		cmsb |= IOM_CTRL_RCV;
+		/* fall through */
 	case ISDN_P_B_L2DTMF:
 		if (test_bit(FLG_DTMFSEND, &ch->bch.Flags))
 			cmsb |= IOM_CTRL_RCV;
@@ -1560,6 +1563,7 @@ isar_l2l1(struct mISDNchannel *ch, struct sk_buff *skb)
 				ich->is->name, hh->id);
 			ret = -EINVAL;
 		}
+		/* fall through */
 	default:
 		pr_info("%s: %s unknown prim(%x,%x)\n",
 			ich->is->name, __func__, hh->prim, hh->id);