kvm: KVM_CAP_IOMMU only available with device assignment

Fix build with CONFIG_PCI unset by linking KVM_CAP_IOMMU to
device assignment config option.  It has no purpose otherwise.

Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Reported-by: Randy Dunlap <rdunlap@infradead.org>
Acked-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 8747fef..96f914e 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -2544,9 +2544,11 @@
 	case KVM_CAP_PV_MMU:	/* obsolete */
 		r = 0;
 		break;
+#ifdef CONFIG_KVM_DEVICE_ASSIGNMENT
 	case KVM_CAP_IOMMU:
 		r = iommu_present(&pci_bus_type);
 		break;
+#endif
 	case KVM_CAP_MCE:
 		r = KVM_MAX_MCE_BANKS;
 		break;