drm/virtgpu: Delete unnecessary checks before drm_gem_object_unreference_unlocked()

The drm_gem_object_unreference_unlocked() function tests whether
its argument is NULL and then returns immediately.
Thus the test around the calls is not needed.

This issue was detected by using the Coccinelle software.
Signed-off-by: Markus Elfring <elfring@users.sourceforge.net>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/5e3dafff-72bb-e616-e84a-368f78fa66b1@users.sourceforge.net

drivers/gpu/drm/virtio/virtgpu_display.c

@@ -53,8 +53,7 @@ static void virtio_gpu_user_framebuffer_destroy(struct drm_framebuffer *fb)
 	struct virtio_gpu_framebuffer *virtio_gpu_fb
 		= to_virtio_gpu_framebuffer(fb);
 
-	if (virtio_gpu_fb->obj)
-		drm_gem_object_unreference_unlocked(virtio_gpu_fb->obj);
+	drm_gem_object_unreference_unlocked(virtio_gpu_fb->obj);
 	drm_framebuffer_cleanup(fb);
 	kfree(virtio_gpu_fb);
 }
@@ -326,8 +325,7 @@ virtio_gpu_user_framebuffer_create(struct drm_device *dev,
 	ret = virtio_gpu_framebuffer_init(dev, virtio_gpu_fb, mode_cmd, obj);
 	if (ret) {
 		kfree(virtio_gpu_fb);
-		if (obj)
-			drm_gem_object_unreference_unlocked(obj);
+		drm_gem_object_unreference_unlocked(obj);
 		return NULL;
 	}