docs: Note ALLOW_EXPERIMENTAL_API for tunnel offloads.
Tunnel offload APIs have '__rte_experimental' attribute, therefore
available only if ALLOW_EXPERIMENTAL_API is defined. Documente it.
@@ -402,6 +402,10 @@ Supported actions for hardware offload are:
- Clone/output (tnl_push and output) for encapsulating over a tunnel.
- Tunnel pop, for packets received on physical ports.
+.. note::
+ Tunnel offloads are experimental APIs in DPDK. In order to enable it,
+ compile with -DALLOW_EXPERIMENTAL_API.
+
Multiprocess
------------
