crypto/aesni_mb: fix memory leak in DOCSIS session

This patch improves the DOCSIS session creation as follows:
- it validates the security action type as well as the protocol before
  creating a session and now does this validation before allocating the
  session from the mempool

Fixes: fda5216fba55 ("crypto/aesni_mb: support DOCSIS protocol")

Signed-off-by: David Coyle <david.coyle@intel.com>
Acked-by: Pablo de Lara <pablo.de.lara.guarch@intel.com>