net: flow_offload: add flow_block_cb_{priv, incref, decref}()

This patch completes the flow block API to introduce:

* flow_block_cb_priv() to access callback private data.
* flow_block_cb_incref() to bump reference counter on this flow block.
* flow_block_cb_decref() to decrement the reference counter.

These functions are taken from the existing tcf_block_cb_priv(),
tcf_block_cb_incref() and tcf_block_cb_decref().

Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/net/flow_offload.h b/include/net/flow_offload.h
index 563d7dc..3fb9cc4 100644
--- a/include/net/flow_offload.h
+++ b/include/net/flow_offload.h
@@ -281,6 +281,10 @@ void flow_block_cb_free(struct flow_block_cb *block_cb);
 struct flow_block_cb *flow_block_cb_lookup(struct flow_block_offload *offload,
 					   tc_setup_cb_t *cb, void *cb_ident);
 
+void *flow_block_cb_priv(struct flow_block_cb *block_cb);
+void flow_block_cb_incref(struct flow_block_cb *block_cb);
+unsigned int flow_block_cb_decref(struct flow_block_cb *block_cb);
+
 static inline void flow_block_cb_add(struct flow_block_cb *block_cb,
 				     struct flow_block_offload *offload)
 {