hw-error: introduce bmc quiesce state

In certain error scenarios, the BMC will enter quiesce state to indicate
to the operator that the system needs immediate attention.

See the following for more information:
https://gerrit.openbmc-project.xyz/c/openbmc/docs/+/29603

Change-Id: I1f16cf1ddcaa976411fe86eae98cb793ee808bda
Signed-off-by: Andrew Geissler <geissonator@yahoo.com>
diff --git a/xyz/openbmc_project/State/BMC.interface.yaml b/xyz/openbmc_project/State/BMC.interface.yaml
index 76e5fdc..1b61da7 100644
--- a/xyz/openbmc_project/State/BMC.interface.yaml
+++ b/xyz/openbmc_project/State/BMC.interface.yaml
@@ -49,3 +49,8 @@
            UpdateInProgress implies BMC is in firmware update mode. CurrentBMCState
            will be set to "UpdateInProgress" while starting image download and
            reset to Ready, once activation is done or error case during update process.
+       - name: 'Quiesced'
+         description: >
+           Quiesced implies an event has occurred on the system requiring
+           attention by the operator. Review phosphor-logging event logs for
+           the cause.