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 <vkoul@kernel.org>
Cc: dmaengine@vger.kernel.org
Signed-off-by: Rob Herring <robh@kernel.org>
Reviewed-by: Thierry Reding <treding@nvidia.com>
Link: https://lore.kernel.org/r/20211206174231.2298349-1-robh@kernel.orgSigned-off-by: Vinod Koul <vkoul@kernel.org>

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

@@ -10,6 +10,7 @@ maintainers:
   - Vinod Koul <vkoul@kernel.org>
 
 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'
@@ -89,6 +90,9 @@ properties:
       - 64
     description: bus width used for memcpy in bits. FTDMAC020 also accept 64 bits
 
+  resets:
+    maxItems: 1
+
 required:
   - reg
   - interrupts