KVM: lapic: Split out x2apic ldr calculation

Split out the ldr calculation from kvm_apic_set_x2apic_id
since we're about to reuse it in the following patch.
Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Cc: stable@vger.kernel.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/lapic.c

@@ -266,9 +266,14 @@ static inline void kvm_apic_set_ldr(struct kvm_lapic *apic, u32 id)
 	recalculate_apic_map(apic->vcpu->kvm);
 }
 
+static inline u32 kvm_apic_calc_x2apic_ldr(u32 id)
+{
+	return ((id >> 4) << 16) | (1 << (id & 0xf));
+}
+
 static inline void kvm_apic_set_x2apic_id(struct kvm_lapic *apic, u32 id)
 {
-	u32 ldr = ((id >> 4) << 16) | (1 << (id & 0xf));
+	u32 ldr = kvm_apic_calc_x2apic_ldr(id);
 
 	WARN_ON_ONCE(id != apic->vcpu->vcpu_id);