Callback functions must have the correct signature

Change-Id: I642823bdc3c7006a0b719ec1e3a9cd75b2b37253
Signed-off-by: Neale Ranns <nranns@cisco.com>
diff --git a/src/vnet/interface.h b/src/vnet/interface.h
index 5c41859..ec76057 100644
--- a/src/vnet/interface.h
+++ b/src/vnet/interface.h
@@ -131,7 +131,7 @@
 {                                                                       \
  vnet_main_t * vnm = vnet_get_main();                                   \
  _vnet_interface_function_list_elt_t *next;                             \
- if (vnm->tag##_functions[p]->fp == (void *) &f)                        \
+ if (vnm->tag##_functions[p]->fp == f)                                  \
     {                                                                   \
       vnm->tag##_functions[p] =                                         \
         vnm->tag##_functions[p]->next_interface_function;               \
@@ -140,7 +140,7 @@
   next = vnm->tag##_functions[p];                                       \
   while (next->next_interface_function)                                 \
     {                                                                   \
-      if (next->next_interface_function->fp == (void *) &f)             \
+      if (next->next_interface_function->fp == f)                       \
         {                                                               \
           next->next_interface_function =                               \
             next->next_interface_function->next_interface_function;     \