power: Remove legacy wakelock code.

Remove parts of code that use the legacy wakelock
implementation as we make the switch to the upstream
kernel's wakeup sources-based implementation.

Change-Id: Idab9e3dd54e8a256b059c88606c9368f7ddb1c1b
Signed-off-by: Anurag Singh <anursing@codeaurora.org>