Entry: Add EventId property

Add a EventId property unique to this event. This property is to support
Redfish API version v1_1_0 for LogEntry.

There are 2 properties to ID the event.
1. Id - a unique number to identify an event
2. EventId - an optional identifier which is associated with
this event and its implementation defined

Signed-off-by: Vijay Lobo <vijaylobo@gmail.com>
Change-Id: Iae23f78ebac0ce55a3db54ac0c73cbf2e6c05be2
diff --git a/xyz/openbmc_project/Logging/Entry.interface.yaml b/xyz/openbmc_project/Logging/Entry.interface.yaml
index 2f3540e..70e8d6a 100755
--- a/xyz/openbmc_project/Logging/Entry.interface.yaml
+++ b/xyz/openbmc_project/Logging/Entry.interface.yaml
@@ -22,6 +22,14 @@
       type: string
       description: >
           The message description of the error event entry.
+    - name: EventId
+      type: string
+      description: >
+          An implementation-dependent unique identifier for this event. This
+          property is different from Id in the sense that Id is a unique number
+          per event but EventId is an optional identifier that is associated
+          with the event. The content of this property is implementation
+          defined.
     - name: AdditionalData
       type: array[string]
       description: >