prism54: islpci_dev: mark expected switch fall-through

In preparation to enabling -Wimplicit-fallthrough, mark switch cases
where we are expecting to fall through.

Addresses-Coverity-ID: 114947 ("Missing break in switch")
Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>

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

@@ -932,6 +932,7 @@ islpci_set_state(islpci_private *priv, islpci_state_t new_state)
 	switch (new_state) {
 	case PRV_STATE_OFF:
 		priv->state_off++;
+		/* fall through */
 	default:
 		priv->state = new_state;
 		break;