arm64: dts: sprd: Change UMS512 idle-state nodename to match bindings

Fix below dtbs_check warning:

idle-states: 'core-pd' does not match any of the regexes: '^(cpu|cluster)-', 'pinctrl-[0-9]+'

Link: https://lore.kernel.org/r/20231221092824.1169453-3-chunyan.zhang@unisoc.comSigned-off-by: Chunyan Zhang <chunyan.zhang@unisoc.com>

arch/arm64/boot/dts/sprd/ums512.dtsi

@@ -113,7 +113,7 @@ CPU7: cpu@700 {
 
 	idle-states {
 		entry-method = "psci";
-		CORE_PD: core-pd {
+		CORE_PD: cpu-pd {
 			compatible = "arm,idle-state";
 			entry-latency-us = <4000>;
 			exit-latency-us = <4000>;