dt-bindings: soc: samsung: exynos-pmu: gs101: add google,pmu-intr-gen phandle

gs101 requires access to the pmu interrupt generation register region
which is exposed as a syscon. Update the exynos-pmu bindings documentation
to reflect this.

Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Peter Griffin <peter.griffin@linaro.org>
Link: https://lore.kernel.org/r/20250506-contrib-pg-cpu-hotplug-suspend2ram-fixes-v1-v4-2-9f64a2657316@linaro.org


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