x86: dt: Use of_get_cpu_hwid()

Replace open coded parsing of CPU nodes' 'reg' property with
of_get_cpu_hwid().

Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: x86@kernel.org
Cc: "H. Peter Anvin" <hpa@zytor.com>
Signed-off-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20211006164332.1981454-11-robh@kernel.org

arch/x86/kernel/devicetree.c

@@ -139,12 +139,11 @@ static void __init dtb_cpu_setup(void)
 {
 	struct device_node *dn;
 	u32 apic_id, version;
-	int ret;
 
 	version = GET_APIC_VERSION(apic_read(APIC_LVR));
 	for_each_of_cpu_node(dn) {
-		ret = of_property_read_u32(dn, "reg", &apic_id);
-		if (ret < 0) {
+		apic_id = of_get_cpu_hwid(dn, 0);
+		if (apic_id == ~0U) {
 			pr_warn("%pOF: missing local APIC ID\n", dn);
 			continue;
 		}