dt-bindings: arm-smmu: Fix json-schema syntax

Commit 4287861d ("dt-bindings: arm-smmu: Add Tegra186 compatible
string") introduced a jsonschema syntax error as a result of a rebase
gone wrong. Fix it.

Fixes: 4287861d ("dt-bindings: arm-smmu: Add Tegra186 compatible string")
Reported-by: Rob Herring <robh@kernel.org>
Signed-off-by: Thierry Reding <treding@nvidia.com>
Acked-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20210621140036.2879563-1-thierry.reding@gmail.comSigned-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>

Documentation/devicetree/bindings/iommu/arm,smmu.yaml

@@ -52,16 +52,14 @@ properties:
         items:
           - const: marvell,ap806-smmu-500
           - const: arm,mmu-500
-      - description: NVIDIA SoCs that program two ARM MMU-500s identically
-        items:
       - description: NVIDIA SoCs that require memory controller interaction
           and may program multiple ARM MMU-500s identically with the memory
           controller interleaving translations between multiple instances
           for improved performance.
         items:
           - enum:
-              - const: nvidia,tegra194-smmu
-              - const: nvidia,tegra186-smmu
+              - nvidia,tegra194-smmu
+              - nvidia,tegra186-smmu
           - const: nvidia,smmu-500
       - items:
           - const: arm,mmu-500