Logging: Entry: Add timestamp property

Add to each error event entry the time when it was
committed in milliseconds since 1970.

Change-Id: I702b0ca836f8c525b6cb09856ec26350e3ac9773
Signed-off-by: Adriana Kobylak <anoo@us.ibm.com>
diff --git a/xyz/openbmc_project/Logging/Entry.interface.yaml b/xyz/openbmc_project/Logging/Entry.interface.yaml
index 67baa7a..e4758e9 100755
--- a/xyz/openbmc_project/Logging/Entry.interface.yaml
+++ b/xyz/openbmc_project/Logging/Entry.interface.yaml
@@ -10,6 +10,10 @@
       type: uint32
       description: >
           The error event entry id number.
+    - name: Timestamp
+      type: uint64
+      description: >
+          Commit timestamp of the error event entry in milliseconds since 1970.
     - name: Severity
       type: enum[self.Level]
       description: >