crypto: crypto4xx - add prng crypto support

This patch adds support for crypto4xx's ANSI X9.17 Annex C compliant
pseudo random number generator which provides a pseudo random source
for the purpose of generating  Initialization Vectors (IV's) for AES
algorithms to the Packet Engine and other pseudo random number
requirements.

Signed-off-by: Christian Lamparter <chunkeey@gmail.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>