crypto: omap-aes - error handling implementation improved

Previous version had not error handling.
Request could remain uncompleted.

Also in the case of DMA error, FLAGS_INIT is unset
and accelerator will be initialized again.

Buffer size allignment is checked.

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