schemas: Add Decorator.Slot interface

This commit adds `Decorator.Slot` in openbmc-dbus.json with property
`SlotNumber` as described in
https://github.com/openbmc/phosphor-dbus-interfaces/blob/master/yaml\
/xyz/openbmc_project/Inventory/Decorator/Slot.interface.yaml.

This commit also adds `Decorator.Slot` to EMConfig so that the
interface can be configured in Entity Manager configuration file.

Change-Id: I098dc476c224fc7fa77c2969d4d1d31f4d0f7af6
Signed-off-by: Delphine CC Chiu <Delphine_CC_Chiu@wiwynn.com>
diff --git a/schemas/openbmc-dbus.json b/schemas/openbmc-dbus.json
index 10c9ea9..36f4baf 100644
--- a/schemas/openbmc-dbus.json
+++ b/schemas/openbmc-dbus.json
@@ -65,6 +65,16 @@
                             },
                             "required": ["FieldReplaceable", "HotPluggable"],
                             "type": "object"
+                        },
+                        "Slot": {
+                            "additionalProperties": false,
+                            "properties": {
+                                "SlotNumber": {
+                                    "type": ["string", "number"]
+                                }
+                            },
+                            "required": ["SlotNumber"],
+                            "type": "object"
                         }
                     },
                     "Item": {