interface: Remove residual dpdk bonding code

dpdk bonding code was removed in 19.08. However, there are still references
to VNET_SW_INTERFACE_FLAG_BOND_SLAVE which was set by the already removed
code.

Type: fix

Signed-off-by: Steven Luong <sluong@cisco.com>
Change-Id: I949a7281e6273f2733dd7532cc4a3bb4f3ce30de
diff --git a/src/vnet/interface.h b/src/vnet/interface.h
index d3065dc..e6418f9 100644
--- a/src/vnet/interface.h
+++ b/src/vnet/interface.h
@@ -676,7 +676,7 @@
 
   VNET_SW_INTERFACE_FLAG_UNNUMBERED = (1 << 3),
 
-  VNET_SW_INTERFACE_FLAG_BOND_SLAVE = (1 << 4),
+  __VNET_SW_INTERFACE_FLAG_UNUSED2 = (1 << 4),
 
   /* Interface does not appear in CLI/API */
   VNET_SW_INTERFACE_FLAG_HIDDEN = (1 << 5),