s390/vfio: use fallthrough;

Convert the various uses of fallthrough comments to fallthrough;

Done via script
Link: https://lore.kernel.org/lkml/b56602fcf79f849e733e7b521bb0e17895d390fa.1582230379.git.joe.com/

Signed-off-by: Joe Perches <[e-mail]>
Signed-off-by: Heiko Carstens <[e-mail]>
Signed-off-by: Vasily Gorbik <[e-mail]>

drivers/s390/crypto/vfio_ap_ops.c

···
 		case AP_RESPONSE_RESET_IN_PROGRESS:
 			if (!status.irq_enabled)
 				return;
-			/* Fall through */
+			fallthrough;
 		case AP_RESPONSE_BUSY:
 			msleep(20);
 			break;