keyguard: fix-fix layout for sw320dp devices

Default values need to be defined in sw360dp or larger devices will
pick up sw320dp values automatically.

On the maguro device the keyguard isn't properly centered.

- Before http://review.cyanogenmod.org/54758:
    http://i.imgur.com/F6sokhA.jpg
- After http://review.cyanogenmod.org/54758:
    http://i.imgur.com/OdTkZLL.jpg
- With this commit:
    http://i.imgur.com/TThq9da.jpg

Change-Id: Idcc29ec79a12e61b26d2ad5070468e70a8ef39df