crypto: sahara - Add driver for SAHARA2 accelerator.

SAHARA2 HW module is included in the i.MX27 SoC from
Freescale. It is capable of performing cipher algorithms
such as AES, 3DES..., hashing and RNG too.

This driver provides support for AES-CBC and AES-ECB
by now.

Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Javier Martin <javier.martin@vista-silicon.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>