[OpenPower-Firmware] op-build v1.21.2

[Stewart Smith]

Release Notes for OpenPower Firmware v1.21.1
============================================

This is a point release on top of op-build v1.21.

Like v1.21, this release is NOT intended for GA POWER9 platforms, for that,
op-build v2.0 is *required*.

Changes since v1.21:

- skiboot 5.10.2
  - Tie tm-suspend fw-feature and opal_reinit_cpus() together
- kernel: Move to Linux 4.14.24-openpower1

-- 
Stewart Smith
OPAL Architect, IBM.