Expose the device state through an attribute in sysfs and allow to
change it. This is to stop and shutdown a QAT device in order to change
its configuration.

The state attribute has been added to a newly created `qat` attribute
group which will contain all _QAT specific_ attributes.

The logic that implements the sysfs entries is part of a new file,
adf_sysfs.c. This exposes an entry point to allow the driver to create
attributes.

The function that creates the sysfs attributes is called from the probe
function of the driver and not in the state machine init function to
allow the change of states even if the device is in the down state.

In order to restore the device configuration between a transition from
down to up, the function that configures the devices has been abstracted
into the HW data structure.

The `state` attribute is only exposed for qat_4xxx devices.
Signed-off-by: Giovanni Cabiddu <giovanni.cabiddu@intel.com>
Co-developed-by: Tomasz Kowallik <tomaszx.kowalik@intel.com>
Signed-off-by: Tomasz Kowallik <tomaszx.kowalik@intel.com>
Reviewed-by: Adam Guerin <adam.guerin@intel.com>
Reviewed-by: Fiona Trahe <fiona.trahe@intel.com>
Reviewed-by: Wojciech Ziemba <wojciech.ziemba@intel.com>
Reviewed-by: Vladis Dronov <vdronov@redhat.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>