interface: refactor interface capabilities code

Make it shorter to type, easier to debug, make adding callbacks in
future simpler.

Type: improvement
Change-Id: I6cdd6375e36da23bd452a7c7273ff42789e94433
Signed-off-by: Damjan Marion <damarion@cisco.com>
diff --git a/src/vnet/interface_output.c b/src/vnet/interface_output.c
index 659273b..cf64eee 100644
--- a/src/vnet/interface_output.c
+++ b/src/vnet/interface_output.c
@@ -640,8 +640,7 @@
 
   /* if not all three flags IP4_,TCP_,UDP_CKSUM set, do compute them
    * here before sending to the interface */
-  if ((hi->caps & VNET_HW_INTERFACE_CAP_SUPPORTS_TX_CKSUM) !=
-      VNET_HW_INTERFACE_CAP_SUPPORTS_TX_CKSUM)
+  if ((hi->caps & VNET_HW_IF_CAP_TX_CKSUM) != VNET_HW_IF_CAP_TX_CKSUM)
     do_tx_offloads = 1;
 
   // basic processing