crypto: iaa - Add IAA Compression Accelerator Documentation

Because the IAA Compression Accelerator requires significant user
setup in order to be used properly, this adds documentation on the
iaa_crypto driver including setup, usage, and examples.

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