Adjust overlay for Trebuchet

- Config item "is_large_screen" is not needed for grouper
- Please see http://review.cyanogenmod.org/#/c/29745/

Change-Id: I752f374d73de51c54f11b1f47644760b7c54c62a
Merge branch 'cm-10.1' of git://github.com/CyanogenMod/android_device_asus_grouper into cm-10.1