Fix build with CONFIG_PCI unset by linking KVM_CAP_IOMMU to
device assignment config option.  It has no purpose otherwise.
Signed-off-by: NAlex Williamson <alex.williamson@redhat.com>
Reported-by: NRandy Dunlap <rdunlap@infradead.org>
Acked-by: NRandy Dunlap <rdunlap@infradead.org>
Signed-off-by: NMarcelo Tosatti <mtosatti@redhat.com>