crypto/hash-afalg: Implement new hash API

crypto/hash-afalg: Implement new hash API

Updates the afalg hash driver to support the new accumulative
hashing changes as part of the patch series.

Implements opening/closing of contexts, updating hash data
and finalizing the hash digest.

In order to support the update function, a flag needs to be passed
to the kernel via the socket send call (MSG_MORE) to notify it that more
data is to be expected to calculate the hash correctly.
As a result, a new function was added to the iov helper utils to allow
passing a flag to the socket send call.

Signed-off-by: Alejandro Zeise <alejandro.zeise@seagate.com>
[ clg: - Handled qcrypto_afalg_hash_ctx_new() errors in
         qcrypto_afalg_hash_new()
       - Freed alg_name in qcrypto_afalg_hash_new()
       - Reworked qcrypto_afalg_recv_from_kernel()
       - Split iov changes from original patch ]
Signed-off-by: Cédric Le Goater <clg@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>