smb: client: Use SHA-512 library for SMB3.1.1 preauth hash

smb: client: Use SHA-512 library for SMB3.1.1 preauth hash

Convert smb311_update_preauth_hash() to use the SHA-512 library instead
of a "sha512" crypto_shash.  This is simpler and faster.  With the
library there's no need to allocate memory, no need to handle errors,
and the SHA-512 code is accessed directly without inefficient indirect
calls and other unnecessary API overhead.

Remove the call to smb311_crypto_shash_allocate() from
smb311_update_preauth_hash(), since it appears to have been needed only
to allocate the "sha512" crypto_shash.  (It also had the side effect of
allocating the "cmac(aes)" crypto_shash, but that's also done in
generate_key() which is where the AES-CMAC key is initialized.)

For now the "sha512" crypto_shash is still being allocated elsewhere.
It will be removed in a later commit.

Reviewed-by: Stefan Metzmacher <metze@samba.org>
Acked-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Eric Biggers <ebiggers@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>