staging: Sync zcache to latest upstream version
zcache-main: enable zcache by default

Signed-off-by: Paul Reioux <reioux@gmail.com>
zcache-main.c: use MACRO define instead of hardcoded default of lzo

Signed-off-by: Paul Reioux <reioux@gmail.com>
zcache-main: switch to lz4 as default

Signed-off-by: Paul Reioux <reioux@gmail.com>