Documentation: add DebugFS doc for HiSilicon SEC

This Documentation is for HiSilicon SEC DebugFS.
Signed-off-by: Longfang Liu <liulongfang@huawei.com>
Signed-off-by: Kai Ye <yekai13@huawei.com>
Reviewed-by: Zaibo Xu <xuzaibo@huawei.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

Documentation/ABI/testing/debugfs-hisi-sec

+What:           /sys/kernel/debug/hisi_sec/<bdf>/sec_dfx
+Date:           Oct 2019
+Contact:        linux-crypto@vger.kernel.org
+Description:    Dump the debug registers of SEC cores.
+		Only available for PF.
+
+What:           /sys/kernel/debug/hisi_sec/<bdf>/clear_enable
+Date:           Oct 2019
+Contact:        linux-crypto@vger.kernel.org
+Description:    Enabling/disabling of clear action after reading
+		the SEC debug registers.
+		0: disable, 1: enable.
+		Only available for PF, and take no other effect on SEC.
+
+What:           /sys/kernel/debug/hisi_sec/<bdf>/current_qm
+Date:           Oct 2019
+Contact:        linux-crypto@vger.kernel.org
+Description:    One SEC controller has one PF and multiple VFs, each function
+		has a QM. This file can be used to select the QM which below
+		qm refers to.
+		Only available for PF.
+
+What:           /sys/kernel/debug/hisi_sec/<bdf>/qm/qm_regs
+Date:           Oct 2019
+Contact:        linux-crypto@vger.kernel.org
+Description:    Dump of QM related debug registers.
+		Available for PF and VF in host. VF in guest currently only
+		has one debug register.
+
+What:           /sys/kernel/debug/hisi_sec/<bdf>/qm/current_q
+Date:           Oct 2019
+Contact:        linux-crypto@vger.kernel.org
+Description:    One QM of SEC 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_sec/<bdf>/qm/clear_enable
+Date:           Oct 2019
+Contact:        linux-crypto@vger.kernel.org
+Description:    Enabling/disabling of clear action after reading
+		the SEC's QM debug registers.
+		0: disable, 1: enable.
+		Only available for PF, and take no other effect on SEC.