Remove some code that is no longer called now that we make sure never
to invoke the SIMD routine with less that 16 bytes of input.

Reviewed-by: Eric Biggers <ebiggers@kernel.org>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>