msm7x30: use KitKat zRAM setting

CM's compcache has been removed, so we need to migrate to KitKat's
mechanism. The value is set to 128 MB for now, which gets compressed
to ~40 MB on RAM and may provide benefits to multitasking.

Change-Id: Ifdf5be79a07253051f789db459c8958c09a48472