crypto: omap-aes - redundant locking is removed

Submitting request involved double locking for enqueuing and
dequeuing. Now it is done under the same lock.

FLAGS_BUSY is now handled under the same lock.

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