mt76: mt7615: Fix fall-through warnings for Clang

In preparation to enable -Wimplicit-fallthrough for Clang, fix a
warning by replacing a /* fall through */ comment with the new
pseudo-keyword macro fallthrough; instead of letting the code fall
through to the next case.

Notice that Clang doesn't recognize /* fall through */ comments as
implicit fall-through markings.

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

drivers/net/wireless/mediatek/mt76/mt7615/eeprom.c

@@ -127,7 +127,7 @@ mt7615_eeprom_parse_hw_band_cap(struct mt7615_dev *dev)
 		break;
 	case MT_EE_DBDC:
 		dev->dbdc_support = true;
-		/* fall through */
+		fallthrough;
 	default:
 		dev->mphy.cap.has_2ghz = true;
 		dev->mphy.cap.has_5ghz = true;