UPSTREAM: crypto: blake2s - move update and final logic to internal/blake2s.h

Move most of blake2s_update() and blake2s_final() into new inline
functions __blake2s_update() and __blake2s_final() in
include/crypto/internal/blake2s.h so that this logic can be shared by
the shash helper functions.  This will avoid duplicating this logic
between the library and shash implementations.

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

(cherry picked from commit 057edc9c8bb2d5ff5b058b521792c392428a0714)
Bug: 152722841
Bug: 178411248
Change-Id: Idedf8147914839d5280e5d8eec9013264fbb45f9
Signed-off-by: Eric Biggers <ebiggers@google.com>