dt-bindings: mmc: samsung,exynos-dw-mshc: add exynos7870 support

Document the compatibles for Exynos7870's DW MMC driver, for both
non-SMU and SMU variants.

Signed-off-by: Kaustabh Chakraborty <kauschluss@disroot.org>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20250219-exynos7870-mmc-v2-1-b4255a3e39ed@disroot.org
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>

Documentation/devicetree/bindings/mmc/samsung,exynos-dw-mshc.yaml

@@ -24,6 +24,8 @@ properties:
           - samsung,exynos5420-dw-mshc-smu
           - samsung,exynos7-dw-mshc
           - samsung,exynos7-dw-mshc-smu
+          - samsung,exynos7870-dw-mshc
+          - samsung,exynos7870-dw-mshc-smu
       - items:
           - enum:
               - samsung,exynos5433-dw-mshc-smu