exynos_drm_crtc_mode_set assigns primary framebuffer to plane without
taking reference. Then during framebuffer removal it is dereferenced twice,
causing oops. The patch fixes it.
Signed-off-by: NAndrzej Hajda <a.hajda@samsung.com>
Signed-off-by: NInki Dae <inki.dae@samsung.com>
Signed-off-by: NDave Airlie <airlied@redhat.com>