nvme-auth: common: use crypto library in nvme_auth_derive_tls_psk()

nvme-auth: common: use crypto library in nvme_auth_derive_tls_psk()

For the HKDF-Expand-Label computation in nvme_auth_derive_tls_psk(), use
the crypto library instead of crypto_shash and crypto/hkdf.c.

While this means the HKDF "helper" functions are no longer utilized,
they clearly weren't buying us much: it's simpler to just inline the
HMAC computations directly, and this code needs to be tested anyway.  (A
similar result was seen in fs/crypto/.  As a result, this eliminates the
last user of crypto/hkdf.c, which we'll be able to remove as well.)

As usual this is also a lot more efficient, eliminating the allocation
of a transformation object and multiple other dynamic allocations.

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>