hwc: Don't lock eventControl for vsync events

Locking here can lead to a delay in vsync disable/enable
where prepare/set is not yet completed. The HWC spec says that
eventControl needs to take effect immediately.
This lock was earlier present when we waited for SF to unblank
primary at startup and the vsync control ioctls could fail.
This is no longer necessary as we unblank primary on startup now.

Change-Id: I2bf18ae9235f8dd428a495a9a23af7f00f34ff1d
1 file changed