doc: announce ABI change for crypto sym info struct

doc: announce ABI change for crypto sym info struct

Since the API changes made in 17.08, the session mempool
is not created anymore in each crypto device.
Therefore, there is no need to have, in the cryptodev info
structure, the maximum number of sessions supported per device
and per queue pair.

Signed-off-by: Pablo de Lara <pablo.de.lara.guarch@intel.com>
Acked-by: Fiona Trahe <fiona.trahe@intel.com>
Acked-by: Akhil Goyal <akhil.goyal@nxp.com>
Acked-by: Deepak Kumar Jain <deepak.k.jain@intel.com>