Documentation/ABI/testing/sysfs-amd-pmf: Add ABI doc for AMD PMF

AMD PMF driver provides the flexibility to turn "on" or "off"
CnQF feature (introduced in the earlier patch).

Add corresponding ABI documentation for the new sysfs node and
also update MAINTAINERS file with this new information
Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Shyam Sundar S K <Shyam-sundar.S-k@amd.com>
Link: https://lore.kernel.org/r/20220922131202.56529-4-Shyam-sundar.S-k@amd.comSigned-off-by: Hans de Goede <hdegoede@redhat.com>

Documentation/ABI/testing/sysfs-amd-pmf

+What:		/sys/devices/platform/*/cnqf_enable
+Date:		September 2022
+Contact:	Shyam Sundar S K <Shyam-sundar.S-k@amd.com>
+Description:	Reading this file tells if the AMD Platform Management(PMF)
+		Cool n Quiet Framework(CnQF) feature is enabled or not.
+
+		This feature is not enabled by default and gets only turned on
+		if OEM BIOS passes a "flag" to PMF ACPI function (index 11 or 12)
+		or in case the user writes "on".
+
+		To turn off CnQF user can write "off" to the sysfs node.
+		Note: Systems that support auto mode will not have this sysfs file
+		available.

MAINTAINERS

@@ -1026,6 +1026,7 @@ AMD PMF DRIVER
 M:	Shyam Sundar S K <Shyam-sundar.S-k@amd.com>
 L:	platform-driver-x86@vger.kernel.org
 S:	Maintained
+F:	Documentation/ABI/testing/sysfs-amd-pmf
 F:	drivers/platform/x86/amd/pmf/
 
 AMD HSMP DRIVER