vfio-pci: enable by default

CONFIG_VFIO_PCI was not "default y" - and once you do that, it is also
important to disable it if PCI is not there.
Reported-by: NAlex Williamson <alex.williamson@redhat.com>
Tested-by: NAlex Williamson <alex.williamson@redhat.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

hw/vfio/Kconfig

@@ -4,8 +4,9 @@ config VFIO
 
 config VFIO_PCI
     bool
+    default y
     select VFIO
-    depends on LINUX
+    depends on LINUX && PCI
 
 config VFIO_CCW
     bool