Active display: Ability to turn off the screen, when a not clearable notification is present

Removing the last clearable notification in AD turns of the screen. But if there is a not clearable notification, there is no ability to turn it off directly.
This patch adds a power target on place of the 'clear notification' target of AD.

Change-Id: I807cca4c293ed732b441cfdcca50957b427809fa