libmctp: Split padding in pktbuf into header and trailer

The astlpc binding will shortly make use of a medium-specific trailer to
implement a CRC-32 integrity check over packet data. Allow for
medium-specific trailer data in the pktbuf in order to remove the need
for a bounce-buffer. The binding will trim the pktbuf to the payload
length before passing the instance up the stack.

Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
Change-Id: Ib215a552ff218b007f7f119c5235fbc75d9ca6cb
diff --git a/tests/test_cmds.c b/tests/test_cmds.c
index 1772734..057a755 100644
--- a/tests/test_cmds.c
+++ b/tests/test_cmds.c
@@ -63,7 +63,8 @@
 	test_binding->version = 1;
 	test_binding->tx = NULL;
 	test_binding->pkt_size = MCTP_PACKET_SIZE(MCTP_BTU);
-	test_binding->pkt_pad = 0;
+	test_binding->pkt_header = 0;
+	test_binding->pkt_trailer = 0;
 	test_binding->control_rx = control_message_transport_callback;
 	test_binding->control_rx_data = callback_ctx;