futex: Convert to use the preferred 'fallthrough' macro

Signed-off-by: Miaohe Lin <[e-mail]>
Signed-off-by: Ingo Molnar <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]

kernel/futex.c

···
 	switch (cmd) {
 	case FUTEX_WAIT:
 		val3 = FUTEX_BITSET_MATCH_ANY;
-		/* fall through */
+		fallthrough;
 	case FUTEX_WAIT_BITSET:
 		return futex_wait(uaddr, flags, val, timeout, val3);
 	case FUTEX_WAKE:
 		val3 = FUTEX_BITSET_MATCH_ANY;
-		/* fall through */
+		fallthrough;
 	case FUTEX_WAKE_BITSET:
 		return futex_wake(uaddr, flags, val, val3);
 	case FUTEX_REQUEUE: