mpls: migrate old MULTIARCH macros to VLIB_NODE_FN

Change-Id: I8c5f7cda655e3343d50a96d714796ea4255588b6
Signed-off-by: Filip Tehlar <ftehlar@cisco.com>
diff --git a/src/vnet/CMakeLists.txt b/src/vnet/CMakeLists.txt
index 01918ca..e412b45 100644
--- a/src/vnet/CMakeLists.txt
+++ b/src/vnet/CMakeLists.txt
@@ -676,6 +676,13 @@
   mpls/mpls_api.c
 )
 
+list(APPEND VNET_MULTIARCH_SOURCES
+  mpls/mpls_output.c
+  mpls/mpls_input.c
+  mpls/mpls_lookup.c
+  mpls/mpls_features.c
+)
+
 list(APPEND VNET_HEADERS
   mpls/mpls.h
   mpls/mpls_types.h