crypto: x86/blake2s - define shash_alg structs using macros

The shash_alg structs for the four variants of BLAKE2s are identical
except for the algorithm name, driver name, and digest size.  So, avoid
code duplication by using a macro to define these structs.

Acked-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>