schemas: legacy: extract UCD90XXX

Used in [1].

Tested: Schema Validator Pass

References:
[1] https://github.com/openbmc/phosphor-power

Change-Id: I720ddbb497061a710018436fdea7aa4d12c23fa2
Signed-off-by: Alexander Hansen <alexander.hansen@9elements.com>
diff --git a/schemas/global.json b/schemas/global.json
index 31b2333..52657ec 100644
--- a/schemas/global.json
+++ b/schemas/global.json
@@ -139,6 +139,9 @@
                             "$ref": "legacy.json#/$defs/BMC"
                         },
                         {
+                            "$ref": "legacy.json#/$defs/UCD90XXX"
+                        },
+                        {
                             "$ref": "virtual_sensor.json#/$defs/VirtualSensor"
                         },
                         {