Add multi-host postcode support

These changes add the multiple host postcode implementation.
In addition to the LPC snoop the postcode can be read via D-Bus
interface.The same is displayed in seven segment display thorough
GPIO lines.

The design can be refered at
   https://gerrit.openbmc-project.xyz/c/openbmc/docs/+/35065

Tested:

 Verified in Facebook Tiogapass & Yosemitev2 platforms.

1.The postcode displayed in the seven segment corresponding to the
  host position selected in the frontpanel of Facebook
  yosemitev2(4 host).

2.The postcode history is verified in the respective host directory
     "/var/lib/phosphor-post-code-manager/hostX(1,2,3,4)".

Signed-off-by: Kumar Thangavel <thangavel.k@hcl.com>
Change-Id: Id79ad00652bfedd319d3b8ccf1aafbdc60b33d86
7 files changed