Revert "zcache-main: switch to lz4 as default"

This reverts commit 05414e22d5c62efff6be4c6354693b535a3222fd.
Revert "zram_drv: switch default compressor to new lz4"

This reverts commit 440650a7680258df22d568e97d00d5b1a419db89.