dt-bindings: mmc: sdhci-msm: add IPQ6018 compatible

IPQ6018 has a sdhci-msm compatible MMC controller. Add the appropriate
compatible to the documentation.

Signed-off-by: Mantas Pucka <[e-mail]>
Acked-by: Rob Herring <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Ulf Hansson <[e-mail]>

Documentation/devicetree/bindings/mmc/sdhci-msm.yaml

···
           - enum:
               - qcom,ipq5018-sdhci
               - qcom,ipq5332-sdhci
+              - qcom,ipq6018-sdhci
               - qcom,ipq9574-sdhci
               - qcom,qcm2290-sdhci
               - qcom,qcs404-sdhci