ivshmem: remove redundant assignment, fix crash with msi=off

Fix crash when msi=false introduced in 660c97ee (msi_vectors is NULL in
this case)
Signed-off-by: NMarc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: NMarkus Armbruster <armbru@redhat.com>

hw/misc/ivshmem.c

@@ -355,12 +355,9 @@ static CharDriverState* create_eventfd_chr_device(IVShmemState *s,
                                                   int vector)
 {
     /* create a event character device based on the passed eventfd */
-    PCIDevice *pdev = PCI_DEVICE(s);
     int eventfd = event_notifier_get_fd(n);
     CharDriverState *chr;
 
-    s->msi_vectors[vector].pdev = pdev;
-
     chr = qemu_chr_open_eventfd(eventfd);
 
     if (chr == NULL) {