drm/qxl: Replace drm_dev_unref with drm_dev_put

This patch unifies the naming of DRM functions for reference counting
of struct drm_device. The resulting code is more aligned with the rest
of the Linux kernel interfaces.
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Link: http://patchwork.freedesktop.org/patch/msgid/20180713120318.32195-1-tzimmermann@suse.deSigned-off-by: Gerd Hoffmann <kraxel@redhat.com>

drivers/gpu/drm/qxl/qxl_drv.c

@@ -119,7 +119,7 @@ qxl_pci_remove(struct pci_dev *pdev)
 
 	dev->dev_private = NULL;
 	kfree(qdev);
-	drm_dev_unref(dev);
+	drm_dev_put(dev);
 }
 
 static const struct file_operations qxl_fops = {