dt-bindings: riscv: cpus: switch to unevaluatedProperties: false

To permit validation of cpu nodes, swap "additionalProperties: true"
out for "unevaluatedProperties: false".
Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Acked-by: Palmer Dabbelt <palmer@rivosinc.com>
Link: https://lore.kernel.org/r/20230615-viper-stoic-1ff8efd7d51d@spudSigned-off-by: Palmer Dabbelt <palmer@rivosinc.com>

Documentation/devicetree/bindings/riscv/cpus.yaml

@@ -143,7 +143,7 @@ required:
   - riscv,isa
   - interrupt-controller
 
-additionalProperties: true
+unevaluatedProperties: false
 
 examples:
   - |