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.org
Signed-off-by: Vinod Koul <vkoul@kernel.org>