dt-bindings: net/dsa: Add spi-peripheral-props.yaml references

dt-bindings: net/dsa: Add spi-peripheral-props.yaml references

SPI peripheral device bindings need to reference spi-peripheral-props.yaml
in order to use various SPI controller specific properties. Otherwise,
the unevaluatedProperties check will reject any controller specific
properties.

Signed-off-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20220531220122.2412711-1-robh@kernel.org