arm64/crypto: remove redundant update of data

Originally found by cppcheck:

[arch/arm64/crypto/sha2-ce-glue.c:153]: (warning) Assignment of
  function parameter has no effect outside the function. Did you
  forget dereferencing it?

Updating data by blocks * SHA256_BLOCK_SIZE at the end of
sha2_finup is redundant code and can be removed.

Acked-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>