[CRYPTO] tcrypt: Use HMAC template and hash interface

This patch converts tcrypt to use the new HMAC template rather than the
hard-coded version of HMAC.  It also converts all digest users to use
the new cipher interface.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>