crypto: omap-aes - DMA initialization fixes for OMAP off mode

DMA parameters for constant data were initialized during driver probe().
It seems that those settings sometimes are lost when devices goes to off mode.
This patch makes DMA initialization just before use.
It solves off mode problems.

Signed-off-by: Dmitry Kasatkin <dmitry.kasatkin@nokia.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>