crypto: omap-sham - error handling improved

Introduces DMA error handling.

DMA error is returned as a result code of the hash request.
Clients needs to handle error codes and may repeat hash calculation attempt.

Also in the case of DMA error, SHAM module is set to be re-initialized again.
It significantly improves stability against possible HW failures.

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