dt-bindings: memory-controllers: exynos-srom: Remove unneeded type for reg-io-width

'reg-io-width' property is an enum so there is no need to specify its
type.
Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>
Signed-off-by: Rob Herring <robh@kernel.org>

Documentation/devicetree/bindings/memory-controllers/exynos-srom.yaml

@@ -51,9 +51,7 @@ patternProperties:
         maxItems: 1
 
       reg-io-width:
-        allOf:
-          - $ref: /schemas/types.yaml#/definitions/uint32
-          - enum: [1, 2]
+        enum: [1, 2]
         description:
           Data width in bytes (1 or 2). If omitted, default of 1 is used.