drm/exynos/mixer: fix synchronization check in interlaced mode

drm/exynos/mixer: fix synchronization check in interlaced mode

In case of interlace mode video processor registers and mixer config
register must be check to ensure internal state is in sync with shadow
registers.
This patch fixes page-faults in interlaced mode.

Signed-off-by: Andrzej Hajda <a.hajda@samsung.com>
Signed-off-by: Inki Dae <inki.dae@samsung.com>
[backport of mainline commit 2eced8e917b060587fc8ed46df41c364957a5050]
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Change-Id: I8b09ed165101a7dcccd1d6e7338e0216a27f4481