Revert "staging: zcache: Squash upstream changes"

This reverts commit 13e4bc3bcf0bc24cbd4b7f10f002a149dfb0b11b.

Change-Id: I0558f38c85f4f1175430ad3ee90a28b3842b2714
Merge "Revert "staging: zcache: Squash upstream changes"" into kitkat