e1000e: correctly tear down MSI-X memory regions

MSI-X has been disabled by the time the e1000e device is unrealized, hence
msix_uninit is never called.  This causes the object to be leaked, which
shows up as a RAMBlock with empty name when attempting migration.

Reported-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Cc: Jason Wang <jasowang@redhat.com>
Cc: qemu-stable@nongnu.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Tested-by: Laurent Vivier <lvivier@redhat.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>

hw/net/e1000e.c

@@ -306,7 +306,7 @@ e1000e_init_msix(E1000EState *s)
 static void
 e1000e_cleanup_msix(E1000EState *s)
 {
-    if (msix_enabled(PCI_DEVICE(s))) {
+    if (msix_present(PCI_DEVICE(s))) {
         e1000e_unuse_msix_vectors(s, E1000E_MSIX_VEC_NUM);
         msix_uninit(PCI_DEVICE(s), &s->msix, &s->msix);
     }