powerpc/perf/hv_{gpci, 24x7}: Add documentation of device attributes

gpci and 24x7 expose some device specific attributes. Add some
documentation for them.

Signed-off-by: Cody P Schafer <cody@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

Documentation/ABI/testing/sysfs-bus-event_source-devices-hv_24x7

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+What:		/sys/bus/event_source/devices/hv_24x7/interface/catalog
+Date:		February 2014
+Contact:	Cody P Schafer <cody@linux.vnet.ibm.com>
+Description:
+		Provides access to the binary "24x7 catalog" provided by the
+		hypervisor on POWER7 and 8 systems. This catalog lists events
+		avaliable from the powerpc "hv_24x7" pmu. Its format is
+		documented here:
+		https://raw.githubusercontent.com/jmesmon/catalog-24x7/master/hv-24x7-catalog.h
+
+What:		/sys/bus/event_source/devices/hv_24x7/interface/catalog_length
+Date:		February 2014
+Contact:	Cody P Schafer <cody@linux.vnet.ibm.com>
+Description:
+		A number equal to the length in bytes of the catalog. This is
+		also extractable from the provided binary "catalog" sysfs entry.
+
+What:		/sys/bus/event_source/devices/hv_24x7/interface/catalog_version
+Date:		February 2014
+Contact:	Cody P Schafer <cody@linux.vnet.ibm.com>
+Description:
+		Exposes the "version" field of the 24x7 catalog. This is also
+		extractable from the provided binary "catalog" sysfs entry.

Documentation/ABI/testing/sysfs-bus-event_source-devices-hv_gpci

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+What:		/sys/bus/event_source/devices/hv_gpci/interface/collect_privileged
+Date:		February 2014
+Contact:	Cody P Schafer <cody@linux.vnet.ibm.com>
+Description:
+		'0' if the hypervisor is configured to forbid access to event
+		counters being accumulated by other guests and to physical
+		domain event counters.
+		'1' if that access is allowed.
+
+What:		/sys/bus/event_source/devices/hv_gpci/interface/ga
+Date:		February 2014
+Contact:	Cody P Schafer <cody@linux.vnet.ibm.com>
+Description:
+		0 or 1. Indicates whether we have access to "GA" events (listed
+		in arch/powerpc/perf/hv-gpci.h).
+
+What:		/sys/bus/event_source/devices/hv_gpci/interface/expanded
+Date:		February 2014
+Contact:	Cody P Schafer <cody@linux.vnet.ibm.com>
+Description:
+		0 or 1. Indicates whether we have access to "EXPANDED" events (listed
+		in arch/powerpc/perf/hv-gpci.h).
+
+What:		/sys/bus/event_source/devices/hv_gpci/interface/lab
+Date:		February 2014
+Contact:	Cody P Schafer <cody@linux.vnet.ibm.com>
+Description:
+		0 or 1. Indicates whether we have access to "LAB" events (listed
+		in arch/powerpc/perf/hv-gpci.h).
+
+What:		/sys/bus/event_source/devices/hv_gpci/interface/version
+Date:		February 2014
+Contact:	Cody P Schafer <cody@linux.vnet.ibm.com>
+Description:
+		A number indicating the version of the gpci interface that the
+		hypervisor reports supporting.
+
+What:		/sys/bus/event_source/devices/hv_gpci/interface/kernel_version
+Date:		February 2014
+Contact:	Cody P Schafer <cody@linux.vnet.ibm.com>
+Description:
+		A number indicating the latest version of the gpci interface
+		that the kernel is aware of.