schemas: legacy: constrain 'CpuID'

CpuID appears as an index and cannot be negative.

Tested: Schema Validator Pass

Change-Id: Ia22e695f06d7462e7f0f6fb98866b0d007fc7b35
Signed-off-by: Alexander Hansen <alexander.hansen@9elements.com>
diff --git a/schemas/legacy.json b/schemas/legacy.json
index 597a655..aded4d3 100644
--- a/schemas/legacy.json
+++ b/schemas/legacy.json
@@ -980,7 +980,9 @@
                 "const": "MB Upstream Port"
             },
             "CpuID": {
-                "type": "number"
+                "type": "number",
+                "minimum": 0,
+                "multipleOf": 1
             },
             "CurrScaleFactor": {
                 "type": "number"