Fix multiple issues pointed out by the new compiler

ostd/src/arch/x86/kernel/apic/mod.rs

@@ -195,6 +195,7 @@ impl ApicId {
     /// In x2APIC mode, the 32-bit logical x2APIC ID, which can be read from
     /// LDR, is derived from the 32-bit local x2APIC ID:
     /// Logical x2APIC ID = [(x2APIC ID[19:4] << 16) | (1 << x2APIC ID[3:0])]
+    #[allow(unused)]
     pub fn x2apic_logical_id(&self) -> u32 {
         self.x2apic_logical_cluster_id() << 16 | 1 << self.x2apic_logical_field_id()
     }