crypto: arch/nhpoly1305 - process in explicit 4k chunks

Rather than chunking via PAGE_SIZE, this commit changes the arch
implementations to chunk in explicit 4k parts, so that calculations on
maximum acceptable latency don't suddenly become invalid on platforms
where PAGE_SIZE isn't 4k, such as arm64.

Fixes: 0f961f9f ("crypto: x86/nhpoly1305 - add AVX2 accelerated NHPoly1305")
Fixes: 012c8238 ("crypto: x86/nhpoly1305 - add SSE2 accelerated NHPoly1305")
Fixes: a00fa0c8 ("crypto: arm64/nhpoly1305 - add NEON-accelerated NHPoly1305")
Fixes: 16aae359

 ("crypto: arm/nhpoly1305 - add NEON-accelerated NHPoly1305")
Cc: stable@vger.kernel.org
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Reviewed-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>