crypto: atmel-aes - reduce latency of DMA completion

atmel_aes_dma_callback() now directly calls the 'resume' callback instead
of scheduling the done task, which in turn only calls the very same
'resume' callback.

Signed-off-by: Cyrille Pitchen <cyrille.pitchen@atmel.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>