dt-bindings: mfd: syscon: Allow syscon compatible for mediatek,mt7981-topmisc

Commit a95419f ("dt-bindings: mfd: syscon: Add mt7981-topmisc")
added the mediatek,mt7981-topmisc compatible to the `select` block
which is used only for compatibility with older dtschema, but did
not add it in the actual block allowing to specify the "syscon"
fallback compatible, which is required for such node to do anything
meaningful in the end.

Add the mediatek,mt7981-topmisc compatible in the right list to
allow specifing compatible = "mediatek,mt7981-topmisc", "syscon"
in the relevant devicetree node.

Fixes: a95419f ("dt-bindings: mfd: syscon: Add mt7981-topmisc")
Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@oss.qualcomm.com>
Link: https://patch.msgid.link/20260109114356.36454-1-angelogioacchino.delregno@collabora.com
Signed-off-by: Lee Jones <lee@kernel.org>

Author: AngeloGioacchino Del Regno

Documentation/devicetree/bindings/mfd/syscon.yaml

@@ -197,6 +197,7 @@ properties:
               - mediatek,mt2701-pctl-a-syscfg
               - mediatek,mt2712-pctl-a-syscfg
               - mediatek,mt6397-pctl-pmic-syscfg
+              - mediatek,mt7981-topmisc
               - mediatek,mt7988-topmisc
               - mediatek,mt8135-pctl-a-syscfg
               - mediatek,mt8135-pctl-b-syscfg