core: Fix incorrect EID passed to RX callbacks

We want the source EID, not the destination.

Signed-off-by: Jeremy Kerr <jk@ozlabs.org>
diff --git a/core.c b/core.c
index b0d3f05..c6896d1 100644
--- a/core.c
+++ b/core.c
@@ -266,7 +266,7 @@
 		 * no need to create a message context */
 		len = pkt->end - pkt->mctp_hdr_off - sizeof(struct mctp_hdr);
 		p = pkt->data + pkt->mctp_hdr_off + sizeof(struct mctp_hdr),
-		mctp->message_rx(bus->eid, mctp->message_rx_data, p, len);
+		mctp->message_rx(hdr->src, mctp->message_rx_data, p, len);
 		break;
 
 	case MCTP_HDR_FLAG_SOM: