Revert "some fixes for zcache"

This reverts commit f9e40ea0e1f447c64f0fb37e45f5a7a96b8768ba.
Revert "Disable unnecessary function to avoid compiling error"

This reverts commit 02b9782b83b28eb015b64de3869061f5474d9cfb.
update defconfig
I/O Sched Tuning