dt-bindings: arm: qcom: Document ipq6018-cp01 board

Document the ipq6018-cp01 board. It was missing leading to warning:

arch/arm64/boot/dts/qcom/ipq6018-cp01-c1.dt.yaml: /: compatible: 'oneOf' conditional failed, one must be fixed:
        ['qcom,ipq6018-cp01', 'qcom,ipq6018'] is too short
        ['qcom,ipq6018-cp01', 'qcom,ipq6018'] is too long
        Additional items are not allowed ('qcom,ipq6018' was unexpected)

Signed-off-by: Vinod Koul <vkoul@kernel.org>
Link: https://lore.kernel.org/r/20210308060826.3074234-4-vkoul@kernel.org
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>