Bluetooth: core: Use fallthrough pseudo-keyword

Replace the existing /* fall through */ comments and its variants with
the new pseudo-keyword macro fallthrough[1]. Also, remove unnecessary
fall-through markings when it is the case.

[1] https://www.kernel.org/doc/html/latest/process/deprecated.html?highlight=fallthrough#implicit-switch-case-fall-through

Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
diff --git a/net/bluetooth/smp.c b/net/bluetooth/smp.c
index 6fd9ddb..c5c812e 100644
--- a/net/bluetooth/smp.c
+++ b/net/bluetooth/smp.c
@@ -1658,7 +1658,7 @@ int smp_user_confirm_reply(struct hci_conn *hcon, u16 mgmt_op, __le32 passkey)
 		memset(smp->tk, 0, sizeof(smp->tk));
 		BT_DBG("PassKey: %d", value);
 		put_unaligned_le32(value, smp->tk);
-		/* Fall Through */
+		fallthrough;
 	case MGMT_OP_USER_CONFIRM_REPLY:
 		set_bit(SMP_FLAG_TK_VALID, &smp->flags);
 		break;