bmc-quiesced: introduce bmc service failure state

Introduce a new Quiesced state for the BMC. This state will be entered
when the new obmc-bmc-service-failure.target is started. This target
will be started when a systemd service within the BMC goes into a fail
state and has its OnFailure set to start this target.

The design doc for this new function is at:
  https://gerrit.openbmc-project.xyz/c/openbmc/docs/+/46690

Signed-off-by: Andrew Geissler <geissonator@yahoo.com>
Change-Id: I847aeaf2267709c080cf2fd49aac15506c23e2bb
diff --git a/yaml/xyz/openbmc_project/State/BMC.interface.yaml b/yaml/xyz/openbmc_project/State/BMC.interface.yaml
index 60872dd..fd04397 100644
--- a/yaml/xyz/openbmc_project/State/BMC.interface.yaml
+++ b/yaml/xyz/openbmc_project/State/BMC.interface.yaml
@@ -58,6 +58,12 @@
            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: >
+           BMC firmware is quiesced. The BMC firmware is enabled but either
+           unresponsive or only processing a restricted set of commands. This
+           state may be the result of a service within the BMC going into a
+           failed state.
 
    - name: RebootCause
      description: >