nvme-auth: target: remove obsolete crypto_has_shash() checks

nvme-auth: target: remove obsolete crypto_has_shash() checks

Since nvme-auth is now doing its HMAC computations using the crypto
library, it's guaranteed that all the algorithms actually work.
Therefore, remove the crypto_has_shash() checks which are now obsolete.

However, the caller in nvmet_auth_negotiate() seems to have also been
relying on crypto_has_shash(nvme_auth_hmac_name(host_hmac_id)) to
validate the host_hmac_id.  Therefore, make it validate the ID more
directly by checking whether nvme_auth_hmac_hash_len() returns 0 or not.

Acked-by: Ard Biesheuvel <ardb@kernel.org>
Acked-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Eric Biggers <ebiggers@kernel.org>
Signed-off-by: Keith Busch <kbusch@kernel.org>