dt-bindings: mmc: exynos-dw-mshc: Add support for ARTPEC-8

dt-bindings: mmc: exynos-dw-mshc: Add support for ARTPEC-8

The ARTPEC-8 SoC has a DWMMC controller that is compatible with the
Exynos 7 version v2.70a. The main differences from Exynos 7 is that it
does not support HS400 and has extended data read timeout.

Add compatibility string "axis,artpec8-dw-mshc" for ARTPEC-8.

Signed-off-by: Mårten Lindahl <marten.lindahl@axis.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Acked-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20211220113026.21129-2-marten.lindahl@axis.com
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>