Revert "Merge branch '3.8/zswap' into 3.8/master"

Branch defines zsmalloc twice, depends on second version merged.  Will need to
untangle mess before remerging.

This reverts commit b3012388c462047afbb39b525512a37f9d72be51, reversing
changes made to c645d24e294802fe59bf178ece160e6e42d04f07.