power: add timeout not to permit permanent power lock

power: add timeout not to permit permanent power lock

- If an app requests permanent power lock and does not
  release the powr lock, power comsumption will be increased
  dramatically. This is not good for the platform.

- Now, a timeout is added not to permit permanent power lock.
  Even if an app requests permanent power lock, the api
  adds timeout with maximum lock time (currently 10 minutes)
  internally. If the timeout is expired, the permanent power
  lock is released.

- Only the way to keep the power lock is to use the platform
  apis which use power lock internally. For example, if an
  app plays music using MM apis, the power lock will be kept
  sinc the MM apis request power lock internally.

Change-Id: I3f11df904f61f720081e5ab63e4e4da130dc85dc
Signed-off-by: Taeyoung Kim <ty317.kim@samsung.com>