crtc::mode_fixup callback is required by crtcs which internally use
a different mode than requested by user - case of Exynos Mixer.
Signed-off-by: NAndrzej Hajda <a.hajda@samsung.com>
Reviewed-by: NTobias Jakobi <tjakobi@math.uni-bielefeld.de>
Signed-off-by: NInki Dae <inki.dae@samsung.com>