PM / Runtime: Add new helper function: pm_runtime_status_suspended()
This boolean function simply returns whether or not the runtime status
of the device is 'suspended'. Unlike pm_runtime_suspended(), this
function returns the runtime status whether or not runtime PM for the
device has been disabled or not.
Also add entry to Documentation/power/runtime.txt
Signed-off-by: Kevin Hilman <khilman@ti.com> Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>