dt-bindings: mfd: syscon: Merge Samsung Exynos Sysreg bindings

The Samsung Exynos System Registers (Sysreg) bindings are quite simple -
just additional compatible to the syscon.  They do not have any value so
merge them into generic MFD syscon bindings.
Suggested-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>
Reviewed-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>

Documentation/devicetree/bindings/arm/samsung/sysreg.yaml

-# SPDX-License-Identifier: GPL-2.0
-%YAML 1.2
----
-$id: http://devicetree.org/schemas/arm/samsung/sysreg.yaml#
-$schema: http://devicetree.org/meta-schemas/core.yaml#
-
-title: Samsung S5P/Exynos SoC series System Registers (SYSREG)
-
-maintainers:
-  - Krzysztof Kozlowski <krzk@kernel.org>
-
-# Custom select to avoid matching all nodes with 'syscon'
-select:
-  properties:
-    compatible:
-      contains:
-        enum:
-          - samsung,exynos4-sysreg
-          - samsung,exynos5-sysreg
-  required:
-    - compatible
-
-properties:
-  compatible:
-    allOf:
-      - items:
-          - enum:
-              - samsung,exynos4-sysreg
-              - samsung,exynos5-sysreg
-          - const: syscon
-
-  reg:
-    maxItems: 1
-
-examples:
-  - |
-    syscon@10010000 {
-        compatible = "samsung,exynos4-sysreg", "syscon";
-        reg = <0x10010000 0x400>;
-    };
-
-    syscon@10050000 {
-        compatible = "samsung,exynos5-sysreg", "syscon";
-        reg = <0x10050000 0x5000>;
-    };

Documentation/devicetree/bindings/mfd/syscon.yaml

@@ -40,6 +40,8 @@ properties:
               - allwinner,sun50i-a64-system-controller
               - microchip,sparx5-cpu-syscon
               - mstar,msc313-pmsleep
+              - samsung,exynos4-sysreg
+              - samsung,exynos5-sysreg
 
           - const: syscon