drm/exynos: correct connector->dpms field before resuming

During system suspend after connector switch off its dpms field
is set to connector previous dpms state. To properly resume dpms field
should be set to its actual state (off) before resuming to previous dpms state.

Signed-off-by: Andrzej Hajda <a.hajda@samsung.com>
Signed-off-by: Inki Dae <inki.dae@samsung.com>