crypto: iaa - Add per-cpu workqueue table with rebalancing

The iaa compression/decompression algorithms in later patches need a
way to retrieve an appropriate IAA workqueue depending on how close
the associated IAA device is to the current cpu.

For this purpose, add a per-cpu array of workqueues such that an
appropriate workqueue can be retrieved by simply accessing the per-cpu
array.

Whenever a new workqueue is bound to or unbound from the iaa_crypto
driver, the available workqueues are 'rebalanced' such that work
submitted from a particular CPU is given to the most appropriate
workqueue available.  There currently isn't any way for the user to
tweak the way this is done internally - if necessary, knobs can be
added later for that purpose.  Current best practice is to configure
and bind at least one workqueue for each IAA device, but as long as
there is at least one workqueue configured and bound to any IAA device
in the system, the iaa_crypto driver will work, albeit most likely not
as efficiently.

[ Based on work originally by George Powley, Jing Lin and Kyung Min
Park ]

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