fstab: remove recovery partition, allow custom zram size

* Remove recovery.fstab and dynamically change mmc device name
  for recovery/normal fstab.
* BOARD_ZRAM_SIZE can now be used to customize the zRAM allocation size
* Remove recovery partition, as it doesn't exist on our devices.
  This will fix backup/restore in CWM.

Change-Id: Ia38663d160dcfd6a6bae55a91c4bb2d782bd0534