dt-bindings: mmc: sdhci-msm: Add compatible string for msm8994

Add msm8994 SoC specific compatible strings for qcom-sdhci controller.

Signed-off-by: Petr Vorel <petr.vorel@gmail.com>
Link: https://lore.kernel.org/r/20211223225524.9860-1-pvorel@suse.cz


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