[PADLOCK] Move fast path work into aes_set_key and upper layer

Most of the work done aes_padlock can be done in aes_set_key.  This
means that we only have to do it once when the key changes rather
than every time we perform an encryption or decryption.

This patch also sets cra_alignmask to let the upper layer ensure
that the buffers fed to us are aligned correctly.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>