drm/udl: 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>
Signed-off-by: Sean Paul <seanpaul@chromium.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20180926120212.25359-1-tzimmermann@suse.de

drivers/gpu/drm/udl/udl_drv.c

@@ -94,7 +94,7 @@ static int udl_usb_probe(struct usb_interface *interface,
 	return 0;
 
 err_free:
-	drm_dev_unref(dev);
+	drm_dev_put(dev);
 	return r;
 }