hwmon: Add power meter spec to Documentation/hwmon/sysfs-interface

Update the hwmon sysfs interface documentation to include a specification
for power meters.

Signed-off-by: Darrick J. Wong <djwong@us.ibm.com>
Acked-by: Jean Delvare <khali@linux-fr.org>
Signed-off-by: Mark M. Hoffman <mhoffman@lightlink.com>

Documentation/hwmon/sysfs-interface

@@ -328,6 +328,37 @@ curr[1-*]_input	Current input value
 		Unit: milliampere
 		RO
 
+*********
+* Power *
+*********
+
+power[1-*]_average		Average power use
+				Unit: microWatt
+				RO
+
+power[1-*]_average_highest	Historical average maximum power use
+				Unit: microWatt
+				RO
+
+power[1-*]_average_lowest	Historical average minimum power use
+				Unit: microWatt
+				RO
+
+power[1-*]_input		Instantaneous power use
+				Unit: microWatt
+				RO
+
+power[1-*]_input_highest	Historical maximum power use
+				Unit: microWatt
+				RO
+
+power[1-*]_input_lowest		Historical minimum power use
+				Unit: microWatt
+				RO
+
+power[1-*]_reset_history	Reset input_highest, input_lowest,
+				average_highest and average_lowest.
+				WO
 
 **********
 * Alarms *