crypto: ccree - fix backlog memory leak

Fix brown paper bag bug of not releasing backlog list item buffer
when backlog was consumed causing a memory leak when backlog is
used.

Signed-off-by: Gilad Ben-Yossef <gilad@benyossef.com>
Cc: stable@vger.kernel.org # v4.19+
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>