PM: Fix warning on suspend errors

Fixes the point where we need to complete the power transition when
device suspend fails, so that we don't print warnings about devices
added to the device hierarchy after a failing suspend.

[rjw: Modified changelog.]

Signed-off-by: Romit Dasgupta <romit@ti.com>
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>