[Bionic][SRU][Power] Fix PowerPC 842 hardware compression support

[Manoj Iyer]

Please consider the following SRU to Bionic that was considered by IBM
as a critical fix to nx-842 modules. The patch fixes PowerPC 842 
hardware compression support, that effects workloads like zswap and
others that exploit the 842 hardware compression available on Power
architecture.

A test kernel is available in the PPA ppa:ubuntu-power-triage/lp1827755
and test results posted by IBM is available in Comment #5 in the bug
report (https://bugs.launchpad.net/ubuntu-power-systems/+bug/1827755)

Thanks
Manoj Iyer