carl9170: Use fallthrough pseudo-keyword

Replace the existing /* fall through */ comments and its variants with
the new pseudo-keyword macro fallthrough[1].

[1] https://www.kernel.org/doc/html/v5.7/process/deprecated.html?highlight=fallthrough#implicit-switch-case-fall-throughSigned-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Acked-by: Christian Lamparter <chunkeey@gmail.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/20200821065204.GA24827@embeddedor

drivers/net/wireless/ath/carl9170/rx.c

@@ -766,7 +766,7 @@ static void carl9170_rx_untie_data(struct ar9170 *ar, u8 *buf, int len)
 
 			goto drop;
 		}
-		/* fall through */
+		fallthrough;
 
 	case AR9170_RX_STATUS_MPDU_MIDDLE:
 		/*  These are just data + mac status */

drivers/net/wireless/ath/carl9170/tx.c

@@ -830,12 +830,12 @@ static bool carl9170_tx_rts_check(struct ar9170 *ar,
 	case CARL9170_ERP_AUTO:
 		if (ampdu)
 			break;
-		/* fall through */
+		fallthrough;
 
 	case CARL9170_ERP_MAC80211:
 		if (!(rate->flags & IEEE80211_TX_RC_USE_RTS_CTS))
 			break;
-		/* fall through */
+		fallthrough;
 
 	case CARL9170_ERP_RTS:
 		if (likely(!multi))
@@ -856,7 +856,7 @@ static bool carl9170_tx_cts_check(struct ar9170 *ar,
 	case CARL9170_ERP_MAC80211:
 		if (!(rate->flags & IEEE80211_TX_RC_USE_CTS_PROTECT))
 			break;
-		/* fall through */
+		fallthrough;
 
 	case CARL9170_ERP_CTS:
 		return true;