qxl: better vga init in enter_vga_mode

Ask the vga core to update the display.  Will trigger dpy_gfx_resize
if needed.  More complete than just calling dpy_gfx_resize.
Signed-off-by: NGerd Hoffmann <kraxel@redhat.com>
(cherry picked from commit c099e7aa)
Signed-off-by: NMichael Roth <mdroth@linux.vnet.ibm.com>

hw/qxl.c

@@ -1075,8 +1075,8 @@ static void qxl_enter_vga_mode(PCIQXLDevice *d)
     trace_qxl_enter_vga_mode(d->id);
     qemu_spice_create_host_primary(&d->ssd);
     d->mode = QXL_MODE_VGA;
-    dpy_gfx_resize(d->ssd.ds);
     vga_dirty_log_start(&d->vga);
+    vga_hw_update();
 }
 
 static void qxl_exit_vga_mode(PCIQXLDevice *d)