crypto: dcp - Added support for Freescale's DCP co-processor

This patch enables the DCP crypto functionality on imx28.
Currently, only aes-128-cbc is supported.
Moreover, the dcpboot misc-device, which is used by Freescale's
SDK tools and uses a non-software-readable OTP-key, is added.

Changes of v2:
- ring buffer for hardware-descriptors
- use of ablkcipher walk
- OTP key encryption/decryption via misc-device
  (compatible to Freescale-SDK)
- overall cleanup

The DCP is also capable of sha1/sha256 but I won't be able to add
that anytime soon.
Tested with built-in runtime-self-test, tcrypt and openssl via
cryptodev 1.6 on imx28-evk and a custom built imx28-board.

Signed-off-by: Tobias Rauter <tobias.rauter@gmail.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>