The old offload API is removed in 18.08,
so the library version must be increased,
in order to show the incompatibility with 18.05 one.
Fixes: ab3ce1e0c193 ("ethdev: remove old offload API")
Signed-off-by: Thomas Monjalon <thomas@monjalon.net>
Reviewed-by: Andrew Rybchenko <arybchenko@solarflare.com>