aries | p1: drivers: staging: zram: add lz4 support

This patch Introduce LZ4 compression backend and make it available for
selection. LZ4 support is optional and requires user to set ZRAM_LZ4
config option. The default compression backend is LZO.

Test               LZO             LZ4
----------------------------------------------
Initial write   1642744.62      1317005.09
Rewrite         2498980.88      1800645.16
Read            3957026.38      5877043.75
Re-read         3950997.38      5861847.00
Reverse Read    2937114.56      5047384.00
Stride read     2948163.19      4929587.38
Random read     3292692.69      4880793.62
Mixed workload  1545602.62      3502940.38
Random write    2448039.75      1758786.25
Pwrite          1670051.03      1338329.69
Pread           2530682.00      5097177.62
Fwrite          3232085.62      3275942.56
Fread           6306880.25      6645271.12

LZ4 is a very fast lossless compression algorithm,
providing compression speed at 400 MB/s per core,
scalable with multi-cores CPU. It also features an
extremely fast decoder, with speed in multiple GB/s
per core, typically reaching RAM speed limits on
multi-core systems.

Quick comparison:

single thread, Core i5-3340M @2.7GHz,
using the Open-Source Benchmark by m^2 (v0.14.2)
compiled with GCC v4.6.1 on Linux Ubuntu 64-bits v11.10,
using the Silesia Corpus.

Name            Ratio  C.speed D.speed
                        MB/s    MB/s
LZ4 (r101)      2.084    422    1820
LZO 2.06        2.106    414     600
QuickLZ 1.5.1b6 2.237    373     420
Snappy 1.1.0    2.091    323    1070
LZF             2.077    270     570
zlib 1.2.8 -1   2.730     65     280
LZ4 HC (r101)   2.720     25    2080
zlib 1.2.8 -6   3.099     21     300

Signed-off-by: Humberto Borba <humberos@gmail.com>
Change-Id: I9f3e5d30967019023375413879d55102eff4303a