schema: fix FileMode type

Signed-off-by: Iceber Gu <[email protected]>

Author: Iceber

schema/defs-linux.json

@@ -144,9 +144,7 @@
         },
         "FileMode": {
             "description": "File permissions mode (typically an octal value)",
-            "type": "integer",
-            "minimum": 0,
-            "maximum": 512
+            "$ref": "defs.json#/definitions/uint32"
         },
         "FileType": {
             "description": "Type of a block or special character device",