drm/exynos: fimd: move shadow unprotection position

The C#_EN_F in SHADOWCON register is updated per frame.
So it should be protected by fimd_shadow_protect_win().

Signed-off-by: YoungJun Cho <yj44.cho@samsung.com>
Acked-by: Inki Dae <inki.dae@samsung.com>
Acked-by: Kyungmin Park <kyungmin.park@samsung.com>
Signed-off-by: Inki Dae <inki.dae@samsung.com>