Documentation: power: Fix typo in Documentation/power

This patch fix spelling typos found in Documentation/power.

Signed-off-by: Masanari Iida <standby24x7@gmail.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

Documentation/power/runtime_pm.txt

@@ -229,13 +229,13 @@ defined in include/linux/pm.h:
     - if set, the value of child_count is ignored (but still updated)
 
   unsigned int disable_depth;
-    - used for disabling the helper funcions (they work normally if this is
+    - used for disabling the helper functions (they work normally if this is
       equal to zero); the initial value of it is 1 (i.e. runtime PM is
       initially disabled for all devices)
 
   int runtime_error;
     - if set, there was a fatal error (one of the callbacks returned error code
-      as described in Section 2), so the helper funtions will not work until
+      as described in Section 2), so the helper functions will not work until
       this flag is cleared; this is the error code returned by the failing
       callback
 
@@ -524,7 +524,7 @@ pm_runtime_put_sync_autosuspend()
 5. Runtime PM Initialization, Device Probing and Removal
 
 Initially, the runtime PM is disabled for all devices, which means that the
-majority of the runtime PM helper funtions described in Section 4 will return
+majority of the runtime PM helper functions described in Section 4 will return
 -EAGAIN until pm_runtime_enable() is called for the device.
 
 In addition to that, the initial runtime PM status of all devices is