misc: move osi to plugin

Type: refactor

This patch moves osi into a plugin, and also modifies
the init functions of llc and snap to preserve init
order dependency (llc_init --> osi_init --> snap_init).

While the initial intent was to move osi/llc/snap together
into a single plugin, there exists a dependency on llc
in vnet/ethernet, which would require further refactoring
and testing work.

Change-Id: Ic0eff030ee29c8d316c0e0fe13931451aa193527
Signed-off-by: Hadi Rayan Al-Sandid <halsandi@cisco.com>
diff --git a/src/vnet/snap/snap.c b/src/vnet/snap/snap.c
index 9bee415..bf59942 100644
--- a/src/vnet/snap/snap.c
+++ b/src/vnet/snap/snap.c
@@ -192,8 +192,9 @@
   return vlib_call_init_function (vm, snap_input_init);
 }
 
-VLIB_INIT_FUNCTION (snap_init);
-
+VLIB_INIT_FUNCTION (snap_init) = {
+  .runs_after = VLIB_INITS ("llc_init"),
+};
 
 /*
  * fd.io coding-style-patch-verification: ON