nfp: flower: add missing kdoc

Commit 0115552eac ("nfp: remove false positive offloads
in flower vxlan") missed adding kdoc for a new parameter
of nfp_flower_add_offload().

Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Reviewed-by: Simon Horman <simon.horman@netronome.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/netronome/nfp/flower/offload.c

@@ -315,6 +315,7 @@ err_free_flow:
  * @app:	Pointer to the APP handle
  * @netdev:	netdev structure.
  * @flow:	TC flower classifier offload structure.
+ * @egress:	NFP netdev is the egress.
  *
  * Adds a new flow to the repeated hash structure and action payload.
  *