arm64: dts: apm: Add dedicated syscon poweroff compatibles

syscon nodes should always have dedicated compatible for full/accurate
hardware description.

Link: https://lore.kernel.org/r/20240519-dt-bindings-mfd-syscon-split-v1-8-aaf996e2313a@linaro.org
Signed-off-by: Krzysztof Kozlowski <[email protected]>

Author: krzk

arch/arm64/boot/dts/apm/apm-merlin.dts

@@ -32,7 +32,7 @@
 	};
 
 	poweroff_mbox: poweroff_mbox@10548000 {
-		compatible = "syscon";
+		compatible = "apm,merlin-poweroff-mailbox", "syscon";
 		reg = <0x0 0x10548000 0x0 0x30>;
 	};
 

arch/arm64/boot/dts/apm/apm-mustang.dts

@@ -32,7 +32,7 @@
 	};
 
 	poweroff_mbox: poweroff_mbox@10548000 {
-		compatible = "syscon";
+		compatible = "apm,mustang-poweroff-mailbox", "syscon";
 		reg = <0x0 0x10548000 0x0 0x30>;
 	};