secondary-vga: delete mmio subregions upon exit

93abfc88 introduced a reference cycle in
the vga-pci devices, preventing cleanup of the object upon hotblug.

This patch allows to break the cycle.
Signed-off-by: Nremy.noel <remy.noel@blade-group.com>
Message-id: 20181002121935.23706-1-remy.noel@blade-group.com

[ kraxel: delete the recently added edid region too ]
Signed-off-by: NGerd Hoffmann <kraxel@redhat.com>

hw/display/vga-pci.c

@@ -309,6 +309,14 @@ static void pci_secondary_vga_exit(PCIDevice *dev)
     VGACommonState *s = &d->vga;
 
     graphic_console_close(s->con);
+    memory_region_del_subregion(&d->mmio, &d->mrs[0]);
+    memory_region_del_subregion(&d->mmio, &d->mrs[1]);
+    if (d->flags & (1 << PCI_VGA_FLAG_ENABLE_QEXT)) {
+        memory_region_del_subregion(&d->mmio, &d->mrs[2]);
+    }
+    if (d->flags & (1 << PCI_VGA_FLAG_ENABLE_EDID)) {
+        memory_region_del_subregion(&d->mmio, &d->mrs[3]);
+    }
 }
 
 static void pci_secondary_vga_init(Object *obj)