mt76: mt7921: Fix fall-through warning for Clang

In preparation to enable -Wimplicit-fallthrough for Clang, fix the
following warning by explicitly adding a break statement:

drivers/net/wireless/mediatek/mt76/mt7921/main.c:392:2: warning: unannotated fall-through between switch labels [-Wimplicit-fallthrough]

Link: https://github.com/KSPP/linux/issues/115Signed-off-by: NGustavo A. R. Silva <gustavoars@kernel.org>

drivers/net/wireless/mediatek/mt76/mt7921/main.c

@@ -389,6 +389,7 @@ static int mt7921_set_key(struct ieee80211_hw *hw, enum set_key_cmd cmd,
 	case WLAN_CIPHER_SUITE_WEP104:
 		if (!mvif->wep_sta)
 			return -EOPNOTSUPP;
+		break;
 	case WLAN_CIPHER_SUITE_TKIP:
 	case WLAN_CIPHER_SUITE_CCMP:
 	case WLAN_CIPHER_SUITE_CCMP_256: