crypto: lib - remove __HAVE_ARCH_CRYPTO_MEMNEQ

No architecture actually defines this, so it's unneeded.

Signed-off-by: Eric Biggers <ebiggers@google.com>
Reviewed-by: Jason A. Donenfeld <Jason@zx2c4.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>