crypto: ahash - Set default reqsize from ahash_alg

[ Upstream commit 9e01aaa1 ]

Add a reqsize field to struct ahash_alg and use it to set the
default reqsize so that algorithms with a static reqsize are
not forced to create an init_tfm function.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Sasha Levin <sashal@kernel.org>