cryptodev: remove unused digest-appended feature

cryptodev: remove unused digest-appended feature

The cryptodev API had specified that if the digest address field was
left empty on an authentication operation, then the PMD would assume
the digest was appended to the source or destination data.
This case was not handled at all by most PMDs and incorrectly handled
by the QAT PMD.
As no bugs were raised, it is assumed to be not needed, so this patch
removes it, rather than add handling for the case on all PMDs.
The digest can still be appended to the data, but its
address must now be provided in the op.

Signed-off-by: Fiona Trahe <fiona.trahe@intel.com>
Acked-by: John Griffin <john.griffin@intel.com>