prism54: 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-through

Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/20200821062947.GA10202@embeddedor

drivers/net/wireless/intersil/prism54/isl_38xx.c

@@ -223,7 +223,7 @@ isl38xx_in_queue(isl38xx_control_block *cb, int queue)
 		/* send queues */
 	case ISL38XX_CB_TX_MGMTQ:
 		BUG_ON(delta > ISL38XX_CB_MGMT_QSIZE);
-		/* fall through */
+		fallthrough;
 
 	case ISL38XX_CB_TX_DATA_LQ:
 	case ISL38XX_CB_TX_DATA_HQ:

drivers/net/wireless/intersil/prism54/isl_ioctl.c

@@ -1691,7 +1691,7 @@ static int prism54_get_encodeext(struct net_device *ndev,
 	case DOT11_AUTH_BOTH:
 	case DOT11_AUTH_SK:
 		wrqu->encoding.flags |= IW_ENCODE_RESTRICTED;
-		/* fall through */
+		fallthrough;
 	case DOT11_AUTH_OS:
 	default:
 		wrqu->encoding.flags |= IW_ENCODE_OPEN;

drivers/net/wireless/intersil/prism54/islpci_dev.c

@@ -918,7 +918,7 @@ islpci_set_state(islpci_private *priv, islpci_state_t new_state)
 	switch (new_state) {
 	case PRV_STATE_OFF:
 		priv->state_off++;
-		/* fall through */
+		fallthrough;
 	default:
 		priv->state = new_state;
 		break;