platform/x86/intel/ifs: add ABI documentation for IFS

Add the sysfs attributes in ABI/testing for In-Field Scan.
Reviewed-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Jithu Joseph <jithu.joseph@intel.com>
Co-developed-by: Tony Luck <tony.luck@intel.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>
Acked-by: Hans de Goede <hdegoede@redhat.com>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Link: https://lore.kernel.org/r/20220506225410.1652287-12-tony.luck@intel.comSigned-off-by: Hans de Goede <hdegoede@redhat.com>

Documentation/ABI/testing/sysfs-platform-intel-ifs

+What:		/sys/devices/virtual/misc/intel_ifs_<N>/run_test
+Date:		April 21 2022
+KernelVersion:	5.19
+Contact:	"Jithu Joseph" <jithu.joseph@intel.com>
+Description:	Write <cpu#> to trigger IFS test for one online core.
+		Note that the test is per core. The cpu# can be
+		for any thread on the core. Running on one thread
+		completes the test for the core containing that thread.
+		Example: to test the core containing cpu5: echo 5 >
+		/sys/devices/platform/intel_ifs.<N>/run_test
+
+What:		/sys/devices/virtual/misc/intel_ifs_<N>/status
+Date:		April 21 2022
+KernelVersion:	5.19
+Contact:	"Jithu Joseph" <jithu.joseph@intel.com>
+Description:	The status of the last test. It can be one of "pass", "fail"
+		or "untested".
+
+What:		/sys/devices/virtual/misc/intel_ifs_<N>/details
+Date:		April 21 2022
+KernelVersion:	5.19
+Contact:	"Jithu Joseph" <jithu.joseph@intel.com>
+Description:	Additional information regarding the last test. The details file reports
+		the hex value of the SCAN_STATUS MSR. Note that the error_code field
+		may contain driver defined software code not defined in the Intel SDM.
+
+What:		/sys/devices/virtual/misc/intel_ifs_<N>/image_version
+Date:		April 21 2022
+KernelVersion:	5.19
+Contact:	"Jithu Joseph" <jithu.joseph@intel.com>
+Description:	Version (hexadecimal) of loaded IFS binary image. If no scan image
+		is loaded reports "none".
+
+What:		/sys/devices/virtual/misc/intel_ifs_<N>/reload
+Date:		April 21 2022
+KernelVersion:	5.19
+Contact:	"Jithu Joseph" <jithu.joseph@intel.com>
+Description:	Write "1" (or "y" or "Y") to reload the IFS image from
+		/lib/firmware/intel/ifs/ff-mm-ss.scan.