Consolidate following data structures:

skcipher_async_req, aead_async_req -> af_alg_async_req
skcipher_rsgl, aead_rsql -> af_alg_rsgl
skcipher_tsgl, aead_tsql -> af_alg_tsgl
skcipher_ctx, aead_ctx -> af_alg_ctx

Consolidate following functions:

skcipher_sndbuf, aead_sndbuf -> af_alg_sndbuf
skcipher_writable, aead_writable -> af_alg_writable
skcipher_rcvbuf, aead_rcvbuf -> af_alg_rcvbuf
skcipher_readable, aead_readable -> af_alg_readable
aead_alloc_tsgl, skcipher_alloc_tsgl -> af_alg_alloc_tsgl
aead_count_tsgl, skcipher_count_tsgl -> af_alg_count_tsgl
aead_pull_tsgl, skcipher_pull_tsgl -> af_alg_pull_tsgl
aead_free_areq_sgls, skcipher_free_areq_sgls -> af_alg_free_areq_sgls
aead_wait_for_wmem, skcipher_wait_for_wmem -> af_alg_wait_for_wmem
aead_wmem_wakeup, skcipher_wmem_wakeup -> af_alg_wmem_wakeup
aead_wait_for_data, skcipher_wait_for_data -> af_alg_wait_for_data
aead_data_wakeup, skcipher_data_wakeup -> af_alg_data_wakeup
aead_sendmsg, skcipher_sendmsg -> af_alg_sendmsg
aead_sendpage, skcipher_sendpage -> af_alg_sendpage
aead_async_cb, skcipher_async_cb -> af_alg_async_cb
aead_poll, skcipher_poll -> af_alg_poll

Split out the following common code from recvmsg:

af_alg_alloc_areq: allocation of the request data structure for the
cipher operation

af_alg_get_rsgl: creation of the RX SGL anchored in the request data
structure

The following changes to the implementation without affecting the
functionality have been applied to synchronize slightly different code
bases in algif_skcipher and algif_aead:

The wakeup in af_alg_wait_for_data is triggered when either more data
is received or the indicator that more data is to be expected is
released. The first is triggered by user space, the second is
triggered by the kernel upon finishing the processing of data
(i.e. the kernel is ready for more).

af_alg_sendmsg uses size_t in min_t calculation for obtaining len.
Return code determination is consistent with algif_skcipher. The
scope of the variable i is reduced to match algif_aead. The type of the
variable i is switched from int to unsigned int to match algif_aead.

af_alg_sendpage does not contain the superfluous err = 0 from
aead_sendpage.

af_alg_async_cb requires to store the number of output bytes in
areq->outlen before the AIO callback is triggered.

The POLLIN / POLLRDNORM is now set when either not more data is given or
the kernel is supplied with data. This is consistent to the wakeup from
sleep when the kernel waits for data.

The request data structure is extended by the field last_rsgl which
points to the last RX SGL list entry. This shall help recvmsg
implementation to chain the RX SGL to other SG(L)s if needed. It is
currently used by algif_aead which chains the tag SGL to the RX SGL
during decryption.

Signed-off-by: Stephan Mueller <smueller@chronox.de>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>