core: Free packet in mctp_bus_rx

Change mctp_bus_rx to take ownership of a received packet, freeing it
after use.

This prevents potential leaks in binding implementations.

Signed-off-by: Jeremy Kerr <jk@ozlabs.org>
Change-Id: I76c427df7ffa5172e77eccad682325c1376c424f
diff --git a/libmctp.h b/libmctp.h
index f0633e3..ecf78c6 100644
--- a/libmctp.h
+++ b/libmctp.h
@@ -96,6 +96,10 @@
 
 void mctp_binding_set_tx_enabled(struct mctp_binding *binding, bool enable);
 
+/*
+ * Receive a packet from binding to core. Takes ownership of pkt, free()-ing it
+ * after use.
+ */
 void mctp_bus_rx(struct mctp_binding *binding, struct mctp_pktbuf *pkt);
 
 /* environment-specific allocation */