KVM: x86: check LAPIC presence when building apic_map

We forgot to re-check LAPIC after splitting the loop in commit
173beedc

 (KVM: x86: Software disabled APIC should still deliver
NMIs, 2014-11-02).

Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>
Fixes: 173beedc


Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>