dt-bindings: mmc: sdhci-msm: Add interconnect BW scaling strings

Add interconnect bandwidth scaling supported strings for qcom-sdhci
controller.

Signed-off-by: Pradeep P V K <ppvk@codeaurora.org>
Acked-by: Rob Herring <robh@kernel.org>
Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Link: https://lore.kernel.org/r/1591691846-7578-3-git-send-email-ppvk@codeaurora.org


Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>