crypto: marvell - properly handle CRYPTO_TFM_REQ_MAY_BACKLOG-flagged requests

The mv_cesa_queue_req() function calls crypto_enqueue_request() to
enqueue a request. In the normal case (i.e the queue isn't full), this
function returns -EINPROGRESS. The current Marvell CESA crypto driver
takes this into account and cleans up the request only if an error
occured, i.e if the return value is not -EINPROGRESS.

Unfortunately this causes problems with
CRYPTO_TFM_REQ_MAY_BACKLOG-flagged requests. When such a request is
passed to crypto_enqueue_request() and the queue is full,
crypto_enqueue_request() will return -EBUSY, but will keep the request
enqueued nonetheless. This situation was not properly handled by the
Marvell CESA driver, which was anyway cleaning up the request in such
a situation. When later on the request was taken out of the backlog
and actually processed, a kernel crash occured due to the internal
driver data structures for this structure having been cleaned up.

To avoid this situation, this commit adds a
mv_cesa_req_needs_cleanup() helper function which indicates if the
request needs to be cleaned up or not after a call to
crypto_enqueue_request(). This helper allows to do the cleanup only in
the appropriate cases, and all call sites of mv_cesa_queue_req() are
fixed to use this new helper function.

Reported-by: Vincent Donnefort <vdonnefort@gmail.com>
Fixes: db509a45 ("crypto: marvell/cesa - add TDMA support")
Cc: <stable@vger.kernel.org> # v4.2+
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Acked-by: Boris Brezillon <boris.brezillon@free-electrons.com>
Tested-by: Vincent Donnefort <vdonnefort@gmail.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>