crypto: arm64/sha2-ce - correct digest for empty data in finup

The sha256-ce finup implementation for ARM64 produces wrong digest
for empty input (len=0). Expected: the actual digest, result: initial
value of SHA internal state. The error is in sha256_ce_finup:
for empty data `finalize` will be 1, so the code is relying on
sha2_ce_transform to make the final round. However, in
sha256_base_do_update, the block function will not be called when
len == 0.

Fix it by setting finalize to 0 if data is empty.

Fixes: 03802f6a ("crypto: arm64/sha2-ce - move SHA-224/256 ARMv8 implementation to base layer")
Cc: stable@vger.kernel.org
Signed-off-by: Elena Petrova <lenaptr@google.com>
Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>