dt-bindings: mtd: ti,am654: Prevent unevaluated properties

Reference mtd-physmap.yaml which contains all the relevant properties
for this device. Add "unevaluatedProperties: false" to avoid any
spurious addition of random properties.

Cc: Vignesh Raghavendra <[e-mail]>
Signed-off-by: Miquel Raynal <[e-mail]>
Reviewed-by: Rob Herring <[e-mail]>
Link: https://lore.kernel.org/linux-mtd/[e-mail]

Documentation/devicetree/bindings/mtd/ti,am654-hbmc.yaml

···
 patternProperties:
   "^flash@[0-1],[0-9a-f]+$":
     type: object
+    $ref: mtd-physmap.yaml
+    unevaluatedProperties: false
 
 required:
   - compatible