Software: Add PSU VersionPurpose

Add the new PSU entry in VersionPurpose enum to represent a version for
PSU.

Signed-off-by: Lei YU <mine260309@gmail.com>
Change-Id: I75e048f86db5779b80d00c1e800ae762d2ac6c70
diff --git a/xyz/openbmc_project/Software/Version.interface.yaml b/xyz/openbmc_project/Software/Version.interface.yaml
index f655af0..e769bf7 100644
--- a/xyz/openbmc_project/Software/Version.interface.yaml
+++ b/xyz/openbmc_project/Software/Version.interface.yaml
@@ -30,3 +30,6 @@
         - name: Host
           description: >
             The version is a version for a managed host.
+        - name: PSU
+          description: >
+            The version is a version for a PSU.