drm/mgag200: 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: Markus Elfring <elfring@users.sourceforge.net>
Signed-off-by: Sean Paul <seanpaul@chromium.org>
Link: http://patchwork.freedesktop.org/patch/msgid/05b266e4-2bae-b70b-5a96-ae609496d173@users.sourceforge.net

drivers/gpu/drm/mgag200/mgag200_main.c

@@ -17,8 +17,8 @@
 static void mga_user_framebuffer_destroy(struct drm_framebuffer *fb)
 {
 	struct mga_framebuffer *mga_fb = to_mga_framebuffer(fb);
-	if (mga_fb->obj)
-		drm_gem_object_unreference_unlocked(mga_fb->obj);
+
+	drm_gem_object_unreference_unlocked(mga_fb->obj);
 	drm_framebuffer_cleanup(fb);
 	kfree(fb);
 }