The Cryptographic Engines and Security Accelerators (CESA) supports the
Multi-Packet Chain Mode. With this mode enabled, multiple tdma requests
can be chained and processed by the hardware without software
intervention. This mode was already activated, however the crypto
requests were not chained together. By doing so, we reduce significantly
the number of IRQs. Instead of being interrupted at the end of each
crypto request, we are interrupted at the end of the last cryptographic
request processed by the engine.

This commits re-factorizes the code, changes the code architecture and
adds the required data structures to chain cryptographic requests
together before sending them to an engine (stopped or possibly already
running).
Signed-off-by: NRomain Perier <romain.perier@free-electrons.com>
Acked-by: NBoris Brezillon <boris.brezillon@free-electrons.com>
Signed-off-by: NHerbert Xu <herbert@gondor.apana.org.au>