Retire asynchronous crypto API as it is no longer required by any driver and

Retire asynchronous crypto API as it is no longer required by any driver and
adds unnecessary complexity.  Dedicated crypto offloading devices are not common
anymore.  Modern CPU crypto acceleration works synchronously, eliminating the need
for callbacks.

Replace all occurrences of crypto_dispatch() with crypto_invoke(), which is
blocking and only returns after the operation has completed or an error occured.
Invoke callback functions directly from the consumer (e.g. IPsec, softraid)
instead of relying on the crypto driver to call crypto_done().

ok bluhm@ mvs@ patrick@