crypto: padlock - Switch sha to shash

This patch converts the padlock-sha implementation to shash.
In doing so the existing mechanism of storing the data until
final is no longer viable as we do not have a way of allocating
data in crypto_shash_init and then reliably freeing it.

This is just as well because a better way of handling the problem
is to hash everything but the last chunk using normal sha code
and then provide the intermediate result to the padlock device.

This is good enough because the primary application of padlock-sha
is IPsec and there the data is laid out in the form of an hmac
header followed by the rest of the packet.  In essence we can
provide all the data to the padlock as the hmac header only needs
to be hashed once.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>