crypto: iaa - Add IAA Compression Accelerator stats

Add support for optional debugfs statistics support for the IAA
Compression Accelerator.  This is enabled by the kernel config item:

  CRYPTO_DEV_IAA_CRYPTO_STATS

When enabled, the IAA crypto driver will generate statistics which can
be accessed at /sys/kernel/debug/iaa-crypto/.

See Documentation/driver-api/crypto/iax/iax-crypto.rst for details.

Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>