Revert "crypto: arm64/ARM: NEON accelerated ChaCha20"

This patch reverts the following commits:

8621caa0
80966672

I should not have applied them because they had already been
obsoleted by a subsequent patch series.  They also cause a build
failure because of the subsequent commit 9ae433bc.

Fixes: 9ae433bc ("crypto: chacha20 - convert generic and...")
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>