Add RPC demux component

To support multiple co-located service providers, the rpc_demux
may be used.  It presents a single input rpc_interface and
demultiplexes incoming call requests to 1..* attached outputs
using the interface_id parameter carried by the underlying
RPC.

Signed-off-by: Julian Hall <julian.hall@arm.com>
Change-Id: I03d7423892cd07d8a8fcd445dbb7dc7e62497455
diff --git a/protocols/rpc/common/packed-c/status.h b/protocols/rpc/common/packed-c/status.h
index 3838240..534f0df 100644
--- a/protocols/rpc/common/packed-c/status.h
+++ b/protocols/rpc/common/packed-c/status.h
@@ -25,7 +25,8 @@
     TS_RPC_ERROR_NOT_READY                          = -7,
     TS_RPC_ERROR_INVALID_TRANSACTION                = -8,
     TS_RPC_ERROR_INTERNAL                           = -9,
-    TS_RPC_ERROR_INVALID_PARAMETER                  = -10
+    TS_RPC_ERROR_INVALID_PARAMETER                  = -10,
+    TS_RPC_ERROR_INTERFACE_DOES_NOT_EXIST           = -11
 };
 
 #endif /* PROTOCOLS_RPC_COMMON_STATUS_H */