ARM: dts: mmp2: Add #power-domain-cells to /clocks

The power management unit, described by the soc_clocks node, controls the
power to the peripherals by the means of power domains with a single
cell -- the domain number.

Link: https://lore.kernel.org/r/20200718205019.184927-4-lkundrak@v3.skSigned-off-by: Lubomir Rintel <lkundrak@v3.sk>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>

arch/arm/boot/dts/mmp2.dtsi

@@ -421,6 +421,7 @@ soc_clocks: clocks {
 			reg-names = "mpmu", "apmu", "apbc";
 			#clock-cells = <1>;
 			#reset-cells = <1>;
+			#power-domain-cells = <1>;
 		};
 	};
 };