dt-bindings: hwinfo: samsung,exynos-chipid: add exynos7870-chipid compatible

Document the compatible string "samsung,exynos7870-chipid". The
registers are entirely compatible with "samsung,exynos4210-chipid".

Signed-off-by: Kaustabh Chakraborty <kauschluss@disroot.org>
Link: https://lore.kernel.org/r/20250219-exynos7870-v3-1-e384fb610cad@disroot.org
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>

Author: Kaustabh Chakraborty

Documentation/devicetree/bindings/hwinfo/samsung,exynos-chipid.yaml

@@ -19,6 +19,7 @@ properties:
           - enum:
               - samsung,exynos5433-chipid
               - samsung,exynos7-chipid
+              - samsung,exynos7870-chipid
           - const: samsung,exynos4210-chipid
       - items:
           - enum: