crypto: arm64/crc32 - bring in line with generic CRC32

The arm64 CRC32 (not CRC32c) implementation was not quite doing
the same thing as the generic one. Fix that.

Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Acked-by: Steve Capper <steve.capper@linaro.org>