Romulus to use Virtual PNOR

[Lei YU]

This email is to notify that Romulus is going to use VirtualPNOR feature, if
no objections are received.

It **impacts** to existing Romulus systems, that they must do PNOR code update
when the feature is enabled.

A little background on this topic could be found at:
https://lists.ozlabs.org/pipermail/openbmc/2018-May/011822.html
https://lists.ozlabs.org/pipermail/openbmc/2018-November/014112.html

I did not receive any feedback, so I choose to use VritualPNOR feature,
which has below benefits:
1. It requires minor code changes for a system to switch to VirtualPNOR;
2. It gets full features, including PNOR version, code verification, and code
   update via new interface;
3. When OpenBMC switches to Redfish, it will get Redfish code update for free,
   because IBM will implement Redfish code update based on VirtualPNOR.

The related changes are:
* OpenBMC: https://gerrit.openbmc-project.xyz/#/q/topic:ubifs-pnor-for-romulus
* op-build: https://github.com/open-power/op-build/pull/2578

Any objections?

Thanks!

--
BRs,
Lei YU