change mac address functions take const mac

Change-Id: Ia68db22b917e9af1394c00e5a6b3df134bfd1568
Signed-off-by: Neale Ranns <nranns@cisco.com>
diff --git a/src/vnet/interface_funcs.h b/src/vnet/interface_funcs.h
index 00fc289..a3bfdc9 100644
--- a/src/vnet/interface_funcs.h
+++ b/src/vnet/interface_funcs.h
@@ -344,7 +344,7 @@
 /* Change interface mac address*/
 clib_error_t *vnet_hw_interface_change_mac_address (vnet_main_t * vnm,
 						    u32 hw_if_index,
-						    u8 * mac_address);
+						    const u8 * mac_address);
 
 /* Change rx-mode */
 clib_error_t *set_hw_interface_change_rx_mode (vnet_main_t * vnm,