Documentation: Add debugfs doc for hisi_hpre

Add debugfs descriptions for HiSilicon HPRE driver.
Signed-off-by: Zaibo Xu <xuzaibo@huawei.com>
Signed-off-by: Hui Tang <tanghui20@huawei.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

Documentation/ABI/testing/debugfs-hisi-hpre

+What:           /sys/kernel/debug/hisi_hpre/<bdf>/cluster[0-3]/regs
+Date:           Sep 2019
+Contact:        linux-crypto@vger.kernel.org
+Description:    Dump debug registers from the HPRE cluster.
+		Only available for PF.
+
+What:           /sys/kernel/debug/hisi_hpre/<bdf>/cluster[0-3]/cluster_ctrl
+Date:           Sep 2019
+Contact:        linux-crypto@vger.kernel.org
+Description:    Write the HPRE core selection in the cluster into this file,
+		and then we can read the debug information of the core.
+		Only available for PF.
+
+What:           /sys/kernel/debug/hisi_hpre/<bdf>/rdclr_en
+Date:           Sep 2019
+Contact:        linux-crypto@vger.kernel.org
+Description:    HPRE cores debug registers read clear control. 1 means enable
+		register read clear, otherwise 0. Writing to this file has no
+		functional effect, only enable or disable counters clear after
+		reading of these registers.
+		Only available for PF.
+
+What:           /sys/kernel/debug/hisi_hpre/<bdf>/current_qm
+Date:           Sep 2019
+Contact:        linux-crypto@vger.kernel.org
+Description:    One HPRE controller has one PF and multiple VFs, each function
+		has a QM. Select the QM which below qm refers to.
+		Only available for PF.
+
+What:           /sys/kernel/debug/hisi_hpre/<bdf>/regs
+Date:           Sep 2019
+Contact:        linux-crypto@vger.kernel.org
+Description:    Dump debug registers from the HPRE.
+		Only available for PF.
+
+What:           /sys/kernel/debug/hisi_hpre/<bdf>/qm/qm_regs
+Date:           Sep 2019
+Contact:        linux-crypto@vger.kernel.org
+Description:    Dump debug registers from the QM.
+		Available for PF and VF in host. VF in guest currently only
+		has one debug register.
+
+What:           /sys/kernel/debug/hisi_hpre/<bdf>/qm/current_q
+Date:           Sep 2019
+Contact:        linux-crypto@vger.kernel.org
+Description:    One QM may contain multiple queues. Select specific queue to
+		show its debug registers in above qm_regs.
+		Only available for PF.
+
+What:           /sys/kernel/debug/hisi_hpre/<bdf>/qm/clear_enable
+Date:           Sep 2019
+Contact:        linux-crypto@vger.kernel.org
+Description:    QM debug registers(qm_regs) read clear control. 1 means enable
+		register read clear, otherwise 0.
+		Writing to this file has no functional effect, only enable or
+		disable counters clear after reading of these registers.
+		Only available for PF.