p1: init: zram driver improvements

The comp_algorithm file is read-write and lets to show
available and selected compression algorithms, change
compression algorithm selection (lzo | lz4).

The max_comp_streams file is read-write and specifies the
number of backend's zcomp_strm compression streams (number of
concurrent compress operations) - limits(1-4).

Signed-off-by: Humberto Borba <humberos@gmail.com>
Change-Id: Ia7952ddb4b9f83e33b9b8b787142159c4e34face