dt-bindings: samsung: exynos-pmu: Add compatible for ARTPEC-9 SoC

Add Axis ARTPEC-9 pmu compatible to the bindings documentation.
It reuses the older samsung,exynos7-pmu design.

Signed-off-by: SungMin Park <smn1196@coasia.com>
Signed-off-by: Ravi Patel <ravi.patel@samsung.com>
Acked-by: Conor Dooley <conor.dooley@microchip.com>
Link: https://patch.msgid.link/20251029130731.51305-5-ravi.patel@samsung.com
Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>

Author: SungMin Park

Documentation/devicetree/bindings/soc/samsung/exynos-pmu.yaml

@@ -52,6 +52,7 @@ properties:
           - const: syscon
       - items:
           - enum:
+              - axis,artpec9-pmu
               - samsung,exynos2200-pmu
               - samsung,exynos7870-pmu
               - samsung,exynos7885-pmu