KVM: x86: consolidate different ways to test for in-kernel LAPIC

Different pieces of code checked for vcpu->arch.apic being (non-)NULL,
or used kvm_vcpu_has_lapic (more optimized) or lapic_in_kernel.
Replace everything with lapic_in_kernel's name and kvm_vcpu_has_lapic's
implementation.

Reviewed-by: Radim Krčmář <rkrcmar@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
diff --git a/arch/x86/kvm/pmu.c b/arch/x86/kvm/pmu.c
index 31aa2c8..06ce377 100644
--- a/arch/x86/kvm/pmu.c
+++ b/arch/x86/kvm/pmu.c
@@ -257,7 +257,7 @@
 
 void kvm_pmu_deliver_pmi(struct kvm_vcpu *vcpu)
 {
-	if (vcpu->arch.apic)
+	if (lapic_in_kernel(vcpu))
 		kvm_apic_local_deliver(vcpu->arch.apic, APIC_LVTPC);
 }