dt-bindings: soc: samsung: exynos-sysreg: add clocks for Exynos850

Exynos850 has dedicated clock for accessing SYSREGs.  Allow it, even
though Linux currently does not enable it and relies on bootloader.

Reviewed-by: Rob Herring <robh@kernel.org>
Reviewed-by: Sam Protsenko <semen.protsenko@linaro.org>
Link: https://lore.kernel.org/r/20221127123259.20339-4-krzysztof.kozlowski@linaro.org
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>

Documentation/devicetree/bindings/soc/samsung/samsung,exynos-sysreg.yaml

@@ -36,10 +36,27 @@ properties:
   reg:
     maxItems: 1
 
+  clocks:
+    maxItems: 1
+
 required:
   - compatible
   - reg
 
+allOf:
+  - if:
+      properties:
+        compatible:
+          contains:
+            enum:
+              - samsung,exynos850-sysreg
+    then:
+      required:
+        - clocks
+    else:
+      properties:
+        clocks: false
+
 additionalProperties: false
 
 examples: