hwc: Fix locking.

Remove the unnecessary blank lock, mdp comp lock, secure lock.
Rename the ext lock to a more appropriate draw lock.

The mdp comp lock is at an incorrect place and causes unwanted
objects to show up in dumpsys, since configDone hasnt cleaned
them up yet.

dump(), blank(), draw() should all acquire a common lock.
draw() includes prepare() and set().

Change-Id: I595547dd5a393a8af6cd8c9297d50793b715e658
6 files changed