crypto: qat - add rate limiting feature to qat_4xxx

The Rate Limiting (RL) feature allows to control the rate of requests
that can be submitted on a ring pair (RP). This allows sharing a QAT
device among multiple users while ensuring a guaranteed throughput.

The driver provides a mechanism that allows users to set policies, that
are programmed to the device. The device is then enforcing those policies.

Configuration of RL is accomplished through entities called SLAs
(Service Level Agreement). Each SLA object gets a unique identifier
and defines the limitations for a single service across up to four
ring pairs (RPs count allocated to a single VF).

The rate is determined using two fields:
  * CIR (Committed Information Rate), i.e., the guaranteed rate.
  * PIR (Peak Information Rate), i.e., the maximum rate achievable
    when the device has available resources.
The rate values are expressed in permille scale i.e. 0-1000.
Ring pair selection is achieved by providing a 64-bit mask, where
each bit corresponds to one of the ring pairs.

This adds an interface and logic that allow to add, update, retrieve
and remove an SLA.

Signed-off-by: Damian Muszynski <damian.muszynski@intel.com>
Reviewed-by: Giovanni Cabiddu <giovanni.cabiddu@intel.com>
Reviewed-by: Tero Kristo <tero.kristo@linux.intel.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>