Remove wakelocks from InputReader

The flag EPOLLWAKEUP already guarantees that the system stays awake
while we are processing any events returned by epoll_wait. The system
may only enter suspend after epoll_wait is called again, or if the fd is
removed from epoll.

So, there is no need to do the same wakelock management explicitly in
EventHub/InputReader.

Bug: 141532209
Test: use the power key to turn off/on screen on the device. Play some
music (download some mp3 file), then turn off the screen, and use volume
keys to change the music volume.

Change-Id: I8b3e64300d4f523e28c566cd7d7cd8aef97e0fed