smb: client: Consolidate cmac(aes) shash allocation

Now that smb3_crypto_shash_allocate() and smb311_crypto_shash_allocate()
are identical and only allocate "cmac(aes)", delete the latter and
replace the call to it with the former.

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>