dt-schema expect to have fallback compatible, which is now in-place.

Fixes warning generated by `make qcom/sdm845-oneplus-fajita.dtb`:
arch/arm64/boot/dts/qcom/sdm845-oneplus-fajita.dt.yaml: power-controller@c300000: compatible: ['qcom,sdm845-aoss-qmp'] is too short
        From schema: Documentation/devicetree/bindings/soc/qcom/qcom,aoss-qmp.yaml
Signed-off-by: David Heidelberg <david@ixit.cz>
Komu: David Heidelberg <david@ixit.cz>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Link: https://lore.kernel.org/r/20211220211443.106754-1-david@ixit.cz