schemas: virtual sensor: Add average and sum for calculation sensor

Average and Sum are implemented in phosphor-virtual-sensors [1]. This
commit supports Average and Sum types in schemas.

[1]: https://gerrit.openbmc.org/c/openbmc/phosphor-virtual-sensor/+/74716

Signed-off-by: George Liu <liuxiwei@ieisystem.com>
Change-Id: I726b7a853b5b42bea9c5ea266d5c5a7be6addd83
diff --git a/schemas/virtual_sensor.json b/schemas/virtual_sensor.json
index f4e2e5b..5239b30 100644
--- a/schemas/virtual_sensor.json
+++ b/schemas/virtual_sensor.json
@@ -39,7 +39,13 @@
                 "Type": {
                     "description": "The type of calculation this sensor uses.",
                     "type": "string",
-                    "enum": ["Maximum", "Minimum", "ModifiedMedian"]
+                    "enum": [
+                        "Average",
+                        "Maximum",
+                        "Minimum",
+                        "Sum",
+                        "ModifiedMedian"
+                    ]
                 },
                 "Units": {
                     "description": "The sensor type, as it shows up in the D-Bus object name.",