cryptodev: clarify API for AES-CCM

cryptodev: clarify API for AES-CCM

AES-CCM algorithm has some restrictions when
handling nonce (IV) and AAD information.

As the API stated, the nonce needs to be place 1 byte
after the start of the IV field. This field needs
to be 16 bytes long, regardless the length of the nonce,
but it is important to clarify that the first byte
and the padding added after the nonce may be modified
by the PMDs using this algorithm.

Same happens with the AAD. It needs to be placed 18 bytes
after the start of the AAD field. The field also needs
to be multiple of 16 bytes long and all memory reserved
(the first bytes and the padding (may be modified by the PMDs).

Lastly, nonce is not needed to be placed in the first 16 bytes
of the AAD, as the API stated, as that depends on the PMD
used, so the comment has been removed.

Signed-off-by: Pablo de Lara <pablo.de.lara.guarch@intel.com>
Acked-by: Fiona Trahe <fiona.trahe@intel.com>
Acked-by: Fan Zhang <roy.fan.zhang@intel.com>