memory: pass EventNotifier, not eventfd

Under Win32, EventNotifiers will not have event_notifier_get_fd, so we
cannot call it in common code such as hw/virtio-pci.c.  Pass a pointer to
the notifier, and only retrieve the file descriptor in kvm-specific code.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
diff --git a/xen-all.c b/xen-all.c
index 59f2323..61def2e 100644
--- a/xen-all.c
+++ b/xen-all.c
@@ -560,13 +560,15 @@
 
 static void xen_eventfd_add(MemoryListener *listener,
                             MemoryRegionSection *section,
-                            bool match_data, uint64_t data, int fd)
+                            bool match_data, uint64_t data,
+                            EventNotifier *e)
 {
 }
 
 static void xen_eventfd_del(MemoryListener *listener,
                             MemoryRegionSection *section,
-                            bool match_data, uint64_t data, int fd)
+                            bool match_data, uint64_t data,
+                            EventNotifier *e)
 {
 }