crypto: arm64/crc32 - merge CRC32 and PMULL instruction based drivers

The PMULL based CRC32 implementation already contains code based on the
separate, optional CRC32 instructions to fallback to when operating on
small quantities of data. We can expose these routines directly on systems
that lack the 64x64 PMULL instructions but do implement the CRC32 ones,
which makes the driver that is based solely on those CRC32 instructions
redundant. So remove it.

Note that this aligns arm64 with ARM, whose accelerated CRC32 driver
also combines the CRC32 extension based and the PMULL based versions.

Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Tested-by: Matthias Brugger <mbrugger@suse.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>