Allow flip cover to sleep screen when shut.
Current behavior allows the screen to turn on when the flip
is opened but does not turn off the screen when closed.

Change-Id: Iec3c7fd4cece71360a32c2abae2fe8f76da9e244
Merge branch 'cm-11.0' of https://github.com/CyanogenMod/android_device_oppo_n1 into cd-4.4