ath6kl: 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>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/20200727195111.GA1603@embeddedor

drivers/net/wireless/ath/ath6kl/cfg80211.c

@@ -3897,19 +3897,19 @@ int ath6kl_cfg80211_init(struct ath6kl *ar)
 	switch (ar->hw.cap) {
 	case WMI_11AN_CAP:
 		ht = true;
-		/* fall through */
+		fallthrough;
 	case WMI_11A_CAP:
 		band_5gig = true;
 		break;
 	case WMI_11GN_CAP:
 		ht = true;
-		/* fall through */
+		fallthrough;
 	case WMI_11G_CAP:
 		band_2gig = true;
 		break;
 	case WMI_11AGN_CAP:
 		ht = true;
-		/* fall through */
+		fallthrough;
 	case WMI_11AG_CAP:
 		band_2gig = true;
 		band_5gig = true;

drivers/net/wireless/ath/ath6kl/main.c

@@ -389,7 +389,7 @@ void ath6kl_connect_ap_mode_bss(struct ath6kl_vif *vif, u16 channel)
 		if (!ik->valid || ik->key_type != WAPI_CRYPT)
 			break;
 		/* for WAPI, we need to set the delayed group key, continue: */
-		/* fall through */
+		fallthrough;
 	case WPA_PSK_AUTH:
 	case WPA2_PSK_AUTH:
 	case (WPA_PSK_AUTH | WPA2_PSK_AUTH):