crypto: qat - add rate limiting sysfs interface

Add an interface for the rate limiting feature which allows to add,
remove and modify a QAT SLA (Service Level Agreement).

This adds a new sysfs attr

crypto: qat - add rate limiting sysfs interface

Add an interface for the rate limiting feature which allows to add,
remove and modify a QAT SLA (Service Level Agreement).

This adds a new sysfs attribute group, `qat_rl`, which can be accessed
from /sys/bus/pci/devices/<BUS:DEV:FUNCTION> with the following
hierarchy:
|-+ qat_rl
|---- id (RW) # SLA identifier
|---- cir (RW) # Committed Information Rate
|---- pir (RW) # Peak Information Rate
|---- srv (RW) # Service to be rate limited
|---- rp (RW) (HEX) # Ring pairs to be rate limited
|---- cap_rem (RW) # Remaining capability for a service
|---- sla_op (WO) # Allows to perform an operation on an SLA

The API works by setting the appropriate RW attributes and then
issuing a command through the `sla_op`. For example, to create an SLA, a
user needs to input the necessary data into the attributes cir, pir, srv
and rp and then write into `sla_op` the command `add` to execute the
operation.
The API also provides `cap_rem` attribute to get information about
the remaining device capability within a certain service which is
required when setting an SLA.

Signed-off-by: Ciunas Bennett <[email protected]>
Reviewed-by: Giovanni Cabiddu <[email protected]>
Reviewed-by: Damian Muszynski <[email protected]>
Reviewed-by: Tero Kristo <[email protected]>
Signed-off-by: Herbert Xu <[email protected]>

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