schemas: legacy: extract CFMSensor schema

This allows to remove some properties from 'Aggregate' schema which are
no longer needed, since there is now a more specific schema to use.

Tested: Schema Validator Pass

Change-Id: I2f3372d8d0b58226b06fdb4a0b66453395de8ef4
Signed-off-by: Alexander Hansen <alexander.hansen@9elements.com>
diff --git a/schemas/global.json b/schemas/global.json
index 57bbd61..2bbc023 100644
--- a/schemas/global.json
+++ b/schemas/global.json
@@ -43,6 +43,9 @@
                             "$ref": "legacy.json#/$defs/ExitAirTempSensor"
                         },
                         {
+                            "$ref": "legacy.json#/$defs/CFMSensor"
+                        },
+                        {
                             "$ref": "virtual_sensor.json#/$defs/VirtualSensor"
                         },
                         {