staging: vt6655: Use fallthrough pseudo-keyword

Replace the existing /* fall through */ comments and its variants with
the new pseudo-keyword macro fallthrough[1]. Also, remove unnecessary
fall-through markings when it is the case.

[1] https://www.kernel.org/doc/html/latest/process/deprecated.html?highlight=fallthrough#implicit-switch-case-fall-throughSigned-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Link: https://lore.kernel.org/r/20200707194350.GA3255@embeddedorSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/vt6655/channel.c

@@ -133,7 +133,7 @@ void vnt_init_bands(struct vnt_private *priv)
 
 		priv->hw->wiphy->bands[NL80211_BAND_5GHZ] =
 						&vnt_supported_5ghz_band;
-	/* fallthrough */
+		fallthrough;
 	case RF_RFMD2959:
 	case RF_AIROHA:
 	case RF_AL2230S:

drivers/staging/vt6655/key.c

@@ -51,15 +51,15 @@ static int vnt_set_keymode(struct ieee80211_hw *hw, u8 *mac_addr,
 		/* default key last entry */
 		entry = MAX_KEY_TABLE - 1;
 		key->hw_key_idx = entry;
-		/* fall through */
+		fallthrough;
 	case VNT_KEY_ALLGROUP:
 		key_mode |= VNT_KEY_ALLGROUP;
 		if (onfly_latch)
 			key_mode |= VNT_KEY_ONFLY_ALL;
-		/* fall through */
+		fallthrough;
 	case VNT_KEY_GROUP_ADDRESS:
 		key_mode |= mode;
-		/* fall through */
+		fallthrough;
 	case VNT_KEY_GROUP:
 		key_mode |= (mode << 4);
 		key_mode |= VNT_KEY_GROUP;

drivers/staging/vt6656/channel.c

@@ -145,7 +145,7 @@ void vnt_init_bands(struct vnt_private *priv)
 
 		priv->hw->wiphy->bands[NL80211_BAND_5GHZ] =
 						&vnt_supported_5ghz_band;
-	/* fallthrough */
+		fallthrough;
 	case RF_AL2230:
 	case RF_AL2230S:
 	case RF_VT3226:

drivers/staging/vt6656/key.c

@@ -67,7 +67,7 @@ static int vnt_set_keymode(struct ieee80211_hw *hw, u8 *mac_addr,
 		/* default key last entry */
 		entry = MAX_KEY_TABLE - 1;
 		key->hw_key_idx = entry;
-		/* fall through */
+		fallthrough;
 	case VNT_KEY_GROUP_ADDRESS:
 		key_mode = mode | (mode << 4);
 		break;