firewire: core: WARN on wrong usage of core transaction functions

In the code path which creates request packets, clearly mark a switch
branch which must never be reached with a WARN.

In the code path which creates response packets, replace a BUG by a
friendlier to debug WARN.
Signed-off-by: NStefan Richter <stefanr@s5r6.in-berlin.de>

drivers/firewire/core-transaction.c

@@ -218,6 +218,9 @@ static void fw_fill_request(struct fw_packet *packet, int tcode, int tlabel,
 		packet->header_length = 16;
 		packet->payload_length = 0;
 		break;
+
+	default:
+		WARN(1, KERN_ERR "wrong tcode %d", tcode);
 	}
  common:
 	packet->speed = speed;
@@ -595,8 +598,7 @@ void fw_fill_response(struct fw_packet *response, u32 *request_header,
 		break;
 
 	default:
-		BUG();
-		return;
+		WARN(1, KERN_ERR "wrong tcode %d", tcode);
 	}
 
 	response->payload_bus = 0;