platform/x86: dell-laptop: Mark expected switch fall-throughs

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

Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Signed-off-by: Darren Hart (VMware) <dvhart@infradead.org>

drivers/platform/x86/dell-laptop.c

@@ -1565,8 +1565,10 @@ static ssize_t kbd_led_timeout_store(struct device *dev,
 		switch (unit) {
 		case KBD_TIMEOUT_DAYS:
 			value *= 24;
+			/* fall through */
 		case KBD_TIMEOUT_HOURS:
 			value *= 60;
+			/* fall through */
 		case KBD_TIMEOUT_MINUTES:
 			value *= 60;
 			unit = KBD_TIMEOUT_SECONDS;