crypto: atmel-aes - add debug facilities to monitor register accesses.

This feature should not be enabled in release but can be usefull for
developers who need to monitor register accesses at some specific places.
Set the AES_FLAGS_DUMP_REG flag inside dd->flags to start monitoring the
I/O accesses, clear it to stop monitoring.

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