[lacp] Fix dumping of raw LACP packets

Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/net/eth_slow.c

 	DBGC ( netdev, "SLOW %s %s LACP collector %04x (%d us)\n",
 	       netdev->name, label, ntohs ( lacp->collector.max_delay ),
 	       ( ntohs ( lacp->collector.max_delay ) * 10 ) );
-	DBGC2_HDA ( netdev, 0, iobuf, iob_len ( iobuf ) );
+	DBGC2_HDA ( netdev, 0, iobuf->data, iob_len ( iobuf ) );
 }
 
 /**
 	       ntohs ( marker->marker.port ),
 	       eth_ntoa ( marker->marker.system ),
 	       ntohl ( marker->marker.xact ) );
-	DBGC2_HDA ( netdev, 0, iobuf, iob_len ( iobuf ) );
+	DBGC2_HDA ( netdev, 0, iobuf->data, iob_len ( iobuf ) );
 }
 
 /**