doc: announce crypto device type enumeration removal

doc: announce crypto device type enumeration removal

Refer to RFC patch - cryptodev: remove crypto device type enumeration

It is planned to remove device type enumeration rte_cryptodev_type from
library to remove the coupling between crypto PMD and the librte_cryptodev.

In this case following stuctures will be changed: rte_cryptodev_session,
rte_cryptodev_sym_session, rte_cryptodev_info, rte_cryptodev.

It is planned to change the function rte_cryptodev_count_devtype().
The function prototype doesn’t clearly show the operation.
>From next release 17.08 the dev_type will be changed to driver_id.
So the function name will change to rte_cryptodev_device_count_by_driver().

Signed-off-by: Slawomir Mrozowicz <slawomirx.mrozowicz@intel.com>
Acked-by: Pablo de Lara <pablo.de.lara.guarch@intel.com>
Acked-by: Declan Doherty <declan.doherty@intel.com>
Acked-by: Jerin Jacob <jerin.jacob@caviumnetworks.com>
Acked-by: Fiona Trahe <fiona.trahe@intel.com>
Acked-by: Akhil Goyal <akhil.goyal@nxp.com>