PM: runtime: Add documentation for pm_runtime_resume_and_get()

Commit dd8088d ("PM: runtime: Add pm_runtime_resume_and_get to
deal with usage counter") added a new runtime-PM API function without
updating the documentation in runtime_pm.rst.

Add the missing documentation.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Fixes: dd8088d ("PM: runtime: Add pm_runtime_resume_and_get to deal with usage counter")
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

Author: AlanStern

Documentation/power/runtime_pm.rst

@@ -339,6 +339,10 @@ drivers/base/power/runtime.c and include/linux/pm_runtime.h:
       checked additionally, and -EACCES means that 'power.disable_depth' is
       different from 0
 
+  `int pm_runtime_resume_and_get(struct device *dev);`
+    - run pm_runtime_resume(dev) and if successful, increment the device's
+      usage counter; return the result of pm_runtime_resume
+
   `int pm_request_idle(struct device *dev);`
     - submit a request to execute the subsystem-level idle callback for the
       device (the request is represented by a work item in pm_wq); returns 0 on