rtw88: 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/20200821064959.GA23693@embeddedor

drivers/net/wireless/realtek/rtw88/main.c

@@ -474,10 +474,10 @@ static u8 hw_bw_cap_to_bitamp(u8 bw_cap)
 	case EFUSE_HW_CAP_IGNORE:
 	case EFUSE_HW_CAP_SUPP_BW80:
 		bw |= BIT(RTW_CHANNEL_WIDTH_80);
-		/* fall through */
+		fallthrough;
 	case EFUSE_HW_CAP_SUPP_BW40:
 		bw |= BIT(RTW_CHANNEL_WIDTH_40);
-		/* fall through */
+		fallthrough;
 	default:
 		bw |= BIT(RTW_CHANNEL_WIDTH_20);
 		break;

drivers/net/wireless/realtek/rtw88/phy.c

@@ -1522,7 +1522,7 @@ static u8 rtw_get_channel_group(u8 channel)
 	switch (channel) {
 	default:
 		WARN_ON(1);
-		/* fall through */
+		fallthrough;
 	case 1:
 	case 2:
 	case 36:
@@ -1668,7 +1668,7 @@ static u8 rtw_phy_get_2g_tx_power_index(struct rtw_dev *rtwdev,
 	switch (bandwidth) {
 	default:
 		WARN_ON(1);
-		/* fall through */
+		fallthrough;
 	case RTW_CHANNEL_WIDTH_20:
 		tx_power += pwr_idx_2g->ht_1s_diff.bw20 * factor;
 		if (above_2ss)
@@ -1712,7 +1712,7 @@ static u8 rtw_phy_get_5g_tx_power_index(struct rtw_dev *rtwdev,
 	switch (bandwidth) {
 	default:
 		WARN_ON(1);
-		/* fall through */
+		fallthrough;
 	case RTW_CHANNEL_WIDTH_20:
 		tx_power += pwr_idx_5g->ht_1s_diff.bw20 * factor;
 		if (above_2ss)