Documentation: PM: Clarify pm_runtime_resume_and_get() return value

Update the documentation to match the behaviour of the code.

pm_runtime_resume_and_get() always returns 0 on success, even if
__pm_runtime_resume() returns 1.

Fixes: 2c41233 ("PM: runtime: Add documentation for pm_runtime_resume_and_get()")
Signed-off-by: Paul Barker <paul.barker.ct@bp.renesas.com>
Link: https://patch.msgid.link/20241203143729.478-1-paul.barker.ct@bp.renesas.com
[ rjw: Subject and changelog edits, adjusted new comment formatting ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

Author: pbrkr

Documentation/power/runtime_pm.rst

@@ -347,7 +347,9 @@ drivers/base/power/runtime.c and include/linux/pm_runtime.h:
 
   `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
+      usage counter; returns 0 on success (whether or not the device's
+      runtime PM status was already 'active') or the error code from
+      pm_runtime_resume() on failure.
 
   `int pm_request_idle(struct device *dev);`
     - submit a request to execute the subsystem-level idle callback for the