cpuidle: Add definition of residency to sysfs documentation

Add definition of minimum residency to sysfs documentation and
update the tree to include the residency sysfs entry.
Signed-off-by: Prashanth Prakash <pprakash@codeaurora.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

Documentation/cpuidle/sysfs.txt

@@ -40,6 +40,7 @@ total 0
 -r--r--r-- 1 root root 4096 Feb  8 10:42 latency
 -r--r--r-- 1 root root 4096 Feb  8 10:42 name
 -r--r--r-- 1 root root 4096 Feb  8 10:42 power
+-r--r--r-- 1 root root 4096 Feb  8 10:42 residency
 -r--r--r-- 1 root root 4096 Feb  8 10:42 time
 -r--r--r-- 1 root root 4096 Feb  8 10:42 usage
 
@@ -50,6 +51,7 @@ total 0
 -r--r--r-- 1 root root 4096 Feb  8 10:42 latency
 -r--r--r-- 1 root root 4096 Feb  8 10:42 name
 -r--r--r-- 1 root root 4096 Feb  8 10:42 power
+-r--r--r-- 1 root root 4096 Feb  8 10:42 residency
 -r--r--r-- 1 root root 4096 Feb  8 10:42 time
 -r--r--r-- 1 root root 4096 Feb  8 10:42 usage
 
@@ -60,6 +62,7 @@ total 0
 -r--r--r-- 1 root root 4096 Feb  8 10:42 latency
 -r--r--r-- 1 root root 4096 Feb  8 10:42 name
 -r--r--r-- 1 root root 4096 Feb  8 10:42 power
+-r--r--r-- 1 root root 4096 Feb  8 10:42 residency
 -r--r--r-- 1 root root 4096 Feb  8 10:42 time
 -r--r--r-- 1 root root 4096 Feb  8 10:42 usage
 
@@ -70,6 +73,7 @@ total 0
 -r--r--r-- 1 root root 4096 Feb  8 10:42 latency
 -r--r--r-- 1 root root 4096 Feb  8 10:42 name
 -r--r--r-- 1 root root 4096 Feb  8 10:42 power
+-r--r--r-- 1 root root 4096 Feb  8 10:42 residency
 -r--r--r-- 1 root root 4096 Feb  8 10:42 time
 -r--r--r-- 1 root root 4096 Feb  8 10:42 usage
 --------------------------------------------------------------------------------
@@ -78,6 +82,8 @@ total 0
 * desc : Small description about the idle state (string)
 * disable : Option to disable this idle state (bool) -> see note below
 * latency : Latency to exit out of this idle state (in microseconds)
+* residency : Time after which a state becomes more effecient than any
+  shallower state (in microseconds)
 * name : Name of the idle state (string)
 * power : Power consumed while in this idle state (in milliwatts)
 * time : Total time spent in this idle state (in microseconds)