ramdisk: Increase ZRAM swap size to 192MB

 * Used in CAF for 512MB devices
ramdisk: Remove length parameter for encryption
Set background app limit to 16

 * For low memory devices, the original limit of 24 would be
   impractical anyways since it cannot contain that many apps.

   (from CAF)
Allow more background services

 * Some services or broadcast may get tremendous delay because
   of the limited background services. It will bring about many
   issues like alarmmanagerservice's wakelock held too long.

   (from CAF)