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/pg/stream.c b/src/vnet/pg/stream.c
index 2c75c2b..5f34a43 100644
--- a/src/vnet/pg/stream.c
+++ b/src/vnet/pg/stream.c
@@ -299,7 +299,7 @@
       hi = vnet_get_hw_interface (vnm, pi->hw_if_index);
       if (gso_enabled)
 	{
-	  hi->caps |= VNET_HW_INTERFACE_CAP_SUPPORTS_TCP_GSO;
+	  vnet_hw_if_set_caps (vnm, pi->hw_if_index, VNET_HW_IF_CAP_TCP_GSO);
 	  pi->gso_enabled = 1;
 	  pi->gso_size = gso_size;
 	  if (coalesce_enabled)