spi: dt-bindings: cadence: add missing 'required'

During the conversion the bindings lost list of required properties.

Fixes: aa796868 ("spi: convert Cadence SPI bindings to YAML")
Signed-off-by: NKrzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Reviewed-by: NMichal Simek <michal.simek@amd.com>
Link: https://lore.kernel.org/r/20220704130618.199231-1-krzysztof.kozlowski@linaro.orgSigned-off-by: NMark Brown <broonie@kernel.org>

Documentation/devicetree/bindings/spi/spi-cadence.yaml

@@ -49,6 +49,13 @@ properties:
     enum: [ 0, 1 ]
     default: 0
 
+required:
+  - compatible
+  - reg
+  - interrupts
+  - clock-names
+  - clocks
+
 unevaluatedProperties: false
 
 examples: