dt-bindings: dma: pl08x: Fix unevaluatedProperties warnings

With 'unevaluatedProperties' support implemented, the example has
warnings on primecell properties and 'resets':

Documentation/devicetree/bindings/dma/arm-pl08x.example.dt.yaml: dma-controller@67000000: Unevaluated properties are not allowed ('arm,primecell-periphid', 'resets' were unexpected)

Add the missing reference to primecell.yaml and definition for 'resets'.

Cc: Vinod Koul <[e-mail]>
Cc: [e-mail]
Signed-off-by: Rob Herring <[e-mail]>
Reviewed-by: Thierry Reding <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Vinod Koul <[e-mail]>

Documentation/devicetree/bindings/dma/arm-pl08x.yaml

···
   - Vinod Koul <[e-mail]>
 
 allOf:
+  - $ref: /schemas/arm/primecell.yaml#
   - $ref: "dma-controller.yaml#"
 
 # We need a select here so we don't match all nodes with 'arm,primecell'
···
       - 32
       - 64
     description: bus width used for memcpy in bits. FTDMAC020 also accept 64 bits
+
+  resets:
+    maxItems: 1
 
 required:
   - reg