drm: qxl: Enable atomic modesetting ioctl

Now that atomic support is implemented, enable the atomic flag.
Signed-off-by: NGabriel Krisman Bertazi <krisman@collabora.co.uk>
Link: http://patchwork.freedesktop.org/patch/msgid/20170227204328.18761-15-krisman@collabora.co.ukSigned-off-by: NGerd Hoffmann <kraxel@redhat.com>

drivers/gpu/drm/qxl/qxl_drv.c

@@ -259,7 +259,8 @@ static struct pci_driver qxl_pci_driver = {
 
 static struct drm_driver qxl_driver = {
 	.driver_features = DRIVER_GEM | DRIVER_MODESET | DRIVER_PRIME |
-			   DRIVER_HAVE_IRQ | DRIVER_IRQ_SHARED,
+			   DRIVER_HAVE_IRQ | DRIVER_IRQ_SHARED |
+			   DRIVER_ATOMIC,
 
 	.set_busid = drm_pci_set_busid,