power: validate wakeup source before activating it.

A rogue wakeup source not registered in wakeup_sources list is not visible
from wakeup_sources_stats_show. Check if the wakeup source is registered
properly by looking at the timer struct.

Signed-off-by: jinqian <jinqian@google.com>
Git-repo: https://android.googlesource.com/kernel/common.git


Signed-off-by: Kaushal Kumar <kaushalk@codeaurora.org>
Signed-off-by: Pranav Vashi <neobuddy89@gmail.com>