dt-bindings: pinctrl: samsung: add exynos7870-wakeup-eint compatible

Exynos7870's wakeup pin controller is entirely register-compatible with
Exynos7, thus document the node for Exynos7870 appropriately.

Signed-off-by: Kaustabh Chakraborty <kauschluss@disroot.org>
Link: https://lore.kernel.org/r/20250301-exynos7870-pinctrl-v3-2-ba1da9d3cd2f@disroot.org


Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>