PM / Runtime: pm_runtime_idle() can be called in atomic context

Add to pm_runtime_idle the list of functions that can be called
in atomic context if pm_runtime_irq_safe() has been called for the
device.

Signed-off-by: Ming Lei <tom.leiming@gmail.com>
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>