drm/cirrus: Delete an unnecessary check 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 call is not needed.

This issue was detected by using the Coccinelle software.
Signed-off-by: NMarkus Elfring <elfring@users.sourceforge.net>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/bebf88d8-cc28-657a-e96c-58447d8cf376@users.sourceforge.net

drivers/gpu/drm/cirrus/cirrus_main.c

@@ -17,7 +17,7 @@
 static void cirrus_user_framebuffer_destroy(struct drm_framebuffer *fb)
 {
 	struct cirrus_framebuffer *cirrus_fb = to_cirrus_framebuffer(fb);
-	if (cirrus_fb->obj)
+
 	drm_gem_object_unreference_unlocked(cirrus_fb->obj);
 	drm_framebuffer_cleanup(fb);
 	kfree(fb);