cifs: Convert to use the fallthrough macro

Convert the uses of fallthrough comments to fallthrough macro.
Signed-off-by: Hongxiang Lou <louhongxiang@huawei.com>
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Signed-off-by: Steve French <stfrench@microsoft.com>

fs/cifs/smb2pdu.c

@@ -3913,7 +3913,7 @@ smb2_readv_callback(struct mid_q_entry *mid)
 	case MID_RESPONSE_MALFORMED:
 		credits.value = le16_to_cpu(shdr->CreditRequest);
 		credits.instance = server->reconnect_instance;
-		/* fall through */
+		fallthrough;
 	default:
 		rdata->result = -EIO;
 	}
@@ -4146,7 +4146,7 @@ smb2_writev_callback(struct mid_q_entry *mid)
 	case MID_RESPONSE_MALFORMED:
 		credits.value = le16_to_cpu(rsp->sync_hdr.CreditRequest);
 		credits.instance = server->reconnect_instance;
-		/* fall through */
+		fallthrough;
 	default:
 		wdata->result = -EIO;
 		break;